drm/amdgpu: rename macro for VCN1.0

Rename RREG32_SOC15_DPG_MODE and WREG32_SOC15_DPG_MODE for VCN1.0
These two macros are used specifically for VCN1.0, therefore rename
it from general name to VCN1.0 specific name.

Signed-off-by: Boyuan Zhang <boyuan.zhang@amd.com>
Reviewed-by: James Zhu <james.zhu@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>