Fix cmpli usage in power6 memset.

Building glibc for powerpc64 with recent (2.27.51.20161012) binutils,
with multi-arch enabled, I get the error:

../sysdeps/powerpc/powerpc64/power6/memset.S: Assembler messages:
../sysdeps/powerpc/powerpc64/power6/memset.S:254: Error: operand out of range (5 is not between 0 and 1)
../sysdeps/powerpc/powerpc64/power6/memset.S:254: Error: operand out of range (128 is not between 0 and 31)
../sysdeps/powerpc/powerpc64/power6/memset.S:254: Error: missing operand

Indeed, cmpli is documented as a four-operand instruction, and looking
at nearby code it seems likely cmpldi was intended.  This patch fixes
this powerpc64 code accordingly, and makes a corresponding change to
the powerpc32 code.

Tested for powerpc, powerpc64 and powerpc64le by Tulio Magno Quites
Machado Filho

	* sysdeps/powerpc/powerpc32/power6/memset.S (memset): Use cmplwi
	instead of cmpli.
	* sysdeps/powerpc/powerpc64/power6/memset.S (memset): Use cmpldi
	instead of cmpli.

(cherry picked from commit 78b7adba)