Cleanup the PowerPC tunings to match the new tuning README file.
Default PowerPC to using TUNE_PKGARCH = ${TUNE_PKGARCH_tune-<tune>}
Fix AVAILTUNE settings in ppc603e, and ppce500mc to be addative.
Correct potentially overlapping "spe" definitions in ppce500 and ppce500v2.
(From OE-Core rev: f81f71bcff4bb1032b034b068efe6065113ca9e7)
Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
