salsa20/salsa: hide SP alignment from spadj
The spadj computation in the assembler can't handle SP alignment code
and will just get confused by how it's currently written. Do the
alignment in a scratch register to hide it from the assembler.
Change-Id: I8857f428d96717db29e3a56050f2381bd86807c6
Reviewed-on: https://go-review.googlesource.com/31586
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Adam Langley <agl@golang.org>
Austin Clements