aarch64/strcmp: fix misaligned loop jump target

I accidentally set the loop jump back label as misaligned8 instead of
do_misaligned.  The typo is harmless but it's always nice to not have
to unnecessarily execute those two instructions.

	* sysdeps/aarch64/strcmp.S (do_misaligned): Jump back to
	do_misaligned, not misaligned8.