Merge r323360 into the 6.0 branch : [Hexagon] Accept lowercase b in -hvx-length=64b and -hvx-length=128b

[kparzysz-quic]

Bugzilla Link	36081
Resolution	FIXED
Resolved on	Jan 30, 2018 07:16
Version	6.0
OS	All
Blocks	#35152
CC	@zmodem
Fixed by commit(s)	r323360

Extended Description

Is it OK to merge the following revision(s) to the 6.0 branch?

[kparzysz-quic]

https://reviews.llvm.org/rL323360

[zmodem]

Merged in r323769.