PowerPC64 power8 strncpy cfi fixes

PowerPC64 power8 strncpy cfi fixes

cfi info for stack adjust needs to be on the insn doing the adjust.
cfi describing register saves can be anywhere after the save insn but
before the reg is altered.  Fewer locations with cfi result in smaller
cfi programs and possibly slightly faster exception handling.  Thus
the LR cfi_offset move.

The idea behind ajusting sp after restoring regs is to break a
register dependency chain, in this case not be using r1 immediately
after it is modified.

The missing LR cfi_restore meant that code after the blr,
unaligned_lt_16 and other labels, would have cfi that said LR was at
cfa+16, but that code is reached without LR being saved.

	* sysdeps/powerpc/powerpc64/power8/strncpy.S: Move LR cfi.
	Adjust stack after restoring regs.  Add missing LR cfi_restore.

Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com>