drm/radeon/kms: add additional safe regs for r4xx/rs6xx and r5xx

- r4xx/rs6xx: add support for extended pixel shader
instruction/temp regs
- r5xx: add SM3 regs

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>