drm/amd/amdgpu: Mask rptr as well in ring debugfs

The read/write pointers on sdma4 devices increment
beyond the ring size and should be masked. Tested
on my Ryzen 2400G.

Signed-off-by: Tom St Denis <[e-mail]>
Reviewed-by: Alex Deucher <[e-mail]>
Reviewed-by: Christian König <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c

···
 	result = 0;
 
 	if (*pos < 12) {
-		early[0] = amdgpu_ring_get_rptr(ring);
+		early[0] = amdgpu_ring_get_rptr(ring) & ring->buf_mask;
 		early[1] = amdgpu_ring_get_wptr(ring) & ring->buf_mask;
 		early[2] = ring->wptr & ring->buf_mask;
 		for (i = *pos / 4; i < 3 && size; i++) {