ARM: OMAP2+: clean up some cppcheck warnings

ARM: OMAP2+: clean up some cppcheck warnings

Resolve some warnings identified by cppcheck in arch/arm/mach-omap2:

    [arch/arm/mach-omap2/usb-tusb6010.c:129]: (style) Checking if unsigned variable 'tmp' is less than zero.
    [arch/arm/mach-omap2/prm_common.c:241]: (error) Possible null pointer dereference: irq_setup - otherwise it is redundant to check if irq_setup is null at line 247
    [arch/arm/mach-omap2/pm34xx.c:790]: (style) Variable 'per_clkdm' is assigned a value that is never used
    [arch/arm/mach-omap2/pm34xx.c:790]: (style) Variable 'core_clkdm' is assigned a value that is never used
    [arch/arm/mach-omap2/pm24xx.c:185]: (style) Variable 'only_idle' is assigned a value that is never used
    [arch/arm/mach-omap2/mux.c:254]: (error) Possible null pointer dereference: mux
    [arch/arm/mach-omap2/mux.c:258]: (error) Possible null pointer dereference: mux
    [arch/arm/mach-omap2/gpmc-onenand.c:178]: (style) Variable 'tick_ns' is assigned a value that is never used
    [arch/arm/mach-omap2/gpio.c:56]: (error) Possible null pointer dereference: pdata - otherwise it is redundant to check if pdata is null at line 57
    [arch/arm/mach-omap2/devices.c:45]: (style) Variable 'l' is assigned a value that is never used
    [arch/arm/mach-omap2/board-omap3evm.c:641] -> [arch/arm/mach-omap2/board-omap3evm.c:639]: (style) Found duplicate branches for if and else.
    [arch/arm/mach-omap2/am35xx-emac.c:95]: (style) Variable 'regval' is assigned a value that is never used
    [arch/arm/mach-omap2/devices.c:74]: (style) Variable 'l' is assigned a value that is never used
    [arch/arm/mach-omap2/pm34xx.c:277]: (style) Variable 'per_prev_state' is assigned a value that is never used
    [arch/arm/plat-omap/dmtimer.c:352]: (error) Possible null pointer dereference: timer - otherwise it is redundant to check if timer is null at line 354
    [arch/arm/plat-omap/omap_device.c:478]: (style) Variable 'c' is assigned a value that is never used
    [arch/arm/plat-omap/usb.c:42]: (style) Variable 'status' is assigned a value that is never used
    [arch/arm/mach-omap1/clock.c:197]: (style) Variable 'dpll1_rate' is assigned a value that is never used
    [arch/arm/mach-omap1/lcd_dma.c:60]: (style) struct or union member 'lcd_dma_info::size' is never used
    [arch/arm/mach-omap1/pm.c:572]: (style) Variable 'entry' is assigned a value that is never used

Some of them are pretty good catches, such as gpio.c:56 and
usb-tusb6010.c:129.

Thanks to Jarkko Nikula for some comments on the sscanf() warnings.
It seems that the kernel sscanf() ignores the field width anyway for the
%d format, so those changes have been dropped from this second version.

Thanks to Daniel Marjamäki <daniel.marjamaki@gmail.com> for pointing
out that a variable was unnecessarily marked static in the
board-omap3evm.c change.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: Jarkko Nikula <jarkko.nikula@bitmer.com>
Cc: Charulatha Varadarajan <charu@ti.com>
Cc: Daniel Marjamäki <daniel.marjamaki@gmail.com>
Cc: Tarun Kanti DebBarma <tarun.kanti@ti.com>
Reviewed-by: Charulatha Varadarajan <charu@ti.com> # for gpio.c