x86-64: Optimize L(between_2_3) in memcmp-avx2-movbe.S

Turn

	movzbl	-1(%rdi, %rdx), %edi
	movzbl	-1(%rsi, %rdx), %esi
	orl	%edi, %eax
	orl	%esi, %ecx

into

	movb	-1(%rdi, %rdx), %al
	movb	-1(%rsi, %rdx), %cl

	* sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S (between_2_3):
	Replace movzbl and orl with movb.