Add vload* for addrspace(2) and use as constant load for R600

Signed-off-by: Aaron Watry <awatry@gmail.com>
Reviewed-by: Tom Stellard <thomas.stellard@amd.com>
Enable assembly vload3 int/uint constant/global for R600

It's supported by the R600 LLVM back-end now, at least for evergreen.

Signed-off-by: Aaron Watry <awatry@gmail.com>
Reviewed-by: Tom Stellard <thomas.stellard@amd.com>
Add intN vloadN() implementations for address spaces 3 and 4

Not hooked up to R600 yet due to current lack of support, at least on EG.

Signed-off-by: Aaron Watry <awatry@gmail.com>
Reviewed-by: Tom Stellard <thomas.stellard@amd.com>