drm/amdgpu/sdma7: Implement resume function for each instance

Extracts the resume sequence for per sdma instance from sdma_v7_0_gfx_resume.
This function can be used in start or restart scenarios of specific instances.

Signed-off-by: Jesse Zhang <jesse.zhang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>