Fix the ARM VST4 (single 4-element structure from one lane)

size 16 double-spaced registers instruction printing.

This:
	vld4.16 {d17[1], d19[1], d21[1], d23[1]}, [r7]!

was being printed as:

	vld4.16 {d17[1], d18[1], d19[1], d20[1]}, [r7]!

rdar://16435096

llvm-svn: 204847