drm/amdgpu/gfx: add ring helpers for setting workload profile

Add helpers to switch the workload profile dynamically when
commands are submitted.  This allows us to switch to
the FULLSCREEN3D or COMPUTE profile when work is submitted.
Add a delayed work handler to delay switching out of the
selected profile if additional work comes in.  This works
the same as the VIDEO profile for VCN.  This lets dynamically
enable workload profiles on the fly and then move back
to the default when there is no work.

Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>