R600/SI: Add basic support for more integer vector types.

v1i32, v2i32, v8i32 and v16i32.

Only add VGPR register classes for integer vector types, to avoid attempts
copying from VGPR to SGPR registers, which is not possible.

Patch By: Michel Dänzer

Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Tom Stellard <thomas.stellard@amd.com>
llvm-svn: 174632