conf/machine/include: Cleanup ARM tunings to match README

conf/machine/include: Cleanup ARM tunings to match README

Cleanup the ARM tunings to match the new tunings README file.

The ARM tunings define TUNE_PKGARCH in a way that only one main
arm architecture, i.e. armv6, may be defined at the same time.  We
may have to revise these settings in the future, as well as figure
out a way to better differentiate various optimize tunings in the
package arch.  (This was not done, to preserve existing behavior!)

Fix a number of minor issues w/ the armv5 tunings where DSP variants
were referenced but not defined.

Fix incorrect armv7 entries in armv7a.

Fix PACKAGE_EXTRA_ARCHS definitions inside of tune-cortexm3 and tune-cortexr4.

(From OE-Core rev: 0e71abea5458122188d5eddef2c17147f61ff895)

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>