testsuite, rs6000: Adjust fold-vec-extract-char.p7.c [PR111850]

testsuite, rs6000: Adjust fold-vec-extract-char.p7.c [PR111850]

As PR101169 comment #c4 shows, previsouly the addi count
update on fold-vec-extract-char.p7.c covered a sub-optimal
code gen issue.  On trunk, pass fold-mem-offsets helps to
recover the best code sequence, so this patch is to
revert the count back to the original which matches the
optimal addi count.

	PR testsuite/111850

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/fold-vec-extract-char.p7.c: Update the
	checking count of addi to 6.