drm/amdgpu: Update SDMA scheduler mask handling to include page queue

This patch updates the SDMA scheduler mask handling to include the page queue
if it exists. The scheduler mask is calculated based on the number of SDMA
instances and the presence of the page queue. The mask is updated to reflect
the state of both the SDMA gfx ring and the page queue.

Changes:
- Add handling for the SDMA page queue in `amdgpu_debugfs_sdma_sched_mask_set`.
- Update scheduler mask calculations to include the page queue.
- Modify `amdgpu_debugfs_sdma_sched_mask_get` to return the correct mask value.

This change is necessary to verify multiple queues (SDMA gfx queue + page queue)
and ensure proper scheduling and state management for SDMA 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>