drm/amdgpu: enable context empty interrupt on sdma v4.4.2

With SDMA_CTNL.CTXEMPTY_INT_ENABLE set, the F32 clock can be gated when
SDMA finishes all job and goes to idle.

And no specific interrupt handling is required in driver.

Signed-off-by: Le Ma <le.ma@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>