arm: omap3: Compile lowlevel_init() function only when it is used

arm: omap3: Compile lowlevel_init() function only when it is used

Function lowlevel_init() is called only from cpu_init_crit() and this
function is wrapped into #if .. #endif section. So compile also
lowlevel_init() function under same #if condition.

Function cpy_clk_code() uses lowlevel_init symbol to get address where
go_to_speed code ends. As this symbol is not available anymore when
compiling with CONFIG_SKIP_LOWLEVEL_INIT, defines a new label
go_to_speed_end at the place where go_to_speed code ends.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Acked-by: Pavel Machek <pavel@ucw.cz>