drm/radeon: Allow setting shader registers using DMA/COPY packet3 on SI.

Mesa uses a COPY_DATA packet to copy the grid size for indirect dispatches
into COMPUTE_USER_DATA_*.

Setting those registers with a SET_SH_REG packet is allowed, not allowing
them with other packets seems like an oversight.

v2: Clarify commit message.

Signed-off-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/si.c b/drivers/gpu/drm/radeon/si.c
index 7afe825..b30e719 100644
--- a/drivers/gpu/drm/radeon/si.c
+++ b/drivers/gpu/drm/radeon/si.c
@@ -4364,6 +4364,10 @@
 	if (reg >= 0x28000)
 		return true;
 
+	/* shader regs are also fine */
+	if (reg >= 0xB000 && reg < 0xC000)
+		return true;
+
 	/* check config regs */
 	switch (reg) {
 	case GRBM_GFX_INDEX: