rs6000: Adapt testcases for -mdejagnu-cpu=

rs6000: Adapt testcases for -mdejagnu-cpu=

This is the result of these two oneliners:
perl -ni -e 'print unless /dg-skip-if "do not override -mcpu"/' \
  $(find gcc/testsuite/gcc.target/powerpc/ -type f)
perl -pi -e 's/(dg-options.*)-mcpu=/\1-mdejagnu-cpu=/'  \
  $(find gcc/testsuite/gcc.target/powerpc/ -type f)

gcc/testsuite/
	* gcc.target/powerpc/ throughout: Delete dg-skip-if "do not override
	-mcpu".  Use -mdejagnu-cpu= in dg-options instead of -mcpu=.

From-SVN: r269324