drm/amdgpu/sdma_v7_1: Add missing inst_mask entry in sdma_v7_1_inst_gfx_resume()

drm/amdgpu/sdma_v7_1: Add missing inst_mask entry in sdma_v7_1_inst_gfx_resume()

The comment for sdma_v7_1_inst_gfx_resume() did not include the
inst_mask parameter, even though the function takes it as an argument.

Update the comment to document inst_mask as the mask of SDMA engine
instances to be enabled.

Fixes the below with gcc W=1:
drivers/gpu/drm/amd/amdgpu/sdma_v7_1.c:644 function parameter 'inst_mask' not described in 'sdma_v7_1_inst_gfx_resume'

Cc: Likun Gao <Likun.Gao@amd.com>
Cc: Le Ma <le.ma@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>