Add CS as an alias for HS, and CC as an alias for LO, otherwise

	CSINV	CS, R1, R2, R3

was interpreted as

	CSINV	0, R1, R2, R3

Also fix the corresponding faulty test.

Fixes #12632
Updates #12470

Change-Id: I974cfc7e5ced682d4754ba09b0b102cb08a46567
Reviewed-on: https://go-review.googlesource.com/14680Reviewed-by: Rob Pike <r@golang.org>