S390: Use mvcle for copies > 1MB on 32bit with default memcpy variant.

S390: Use mvcle for copies > 1MB on 32bit with default memcpy variant.

If more than 255 bytes should be copied, the algorithm jumps away.
Before this patch, it jumps to the mvc-loop (.L_G5_12).
Now it jumps first to the "> 1MB" check, which jumps away to
__memcpy_mvcle. Otherwise, the mvc-loop (.L_G5_12) copies the bytes.

ChangeLog:

	* sysdeps/s390/s390-32/memcpy.S (memcpy):
	Jump to 1MB check before executing mvc-loop.