drm/v3d: fix wait for TMU write combiner flush

The hardware sets the TMUWCF bit back to 0 when the TMU write
combiner flush completes so we should be checking for that instead
of the L2TFLS bit.

v2 (Melissa Wen):
  - Add Signed-off-by and Fixes tags.
  - Change the error message for the timeout to be more clear.

Fixes spurious Vulkan CTS failures in:
dEQP-VK.binding_model.descriptorset_random.*

Fixes: d223f98f ("drm/v3d: Add support for compute shader dispatch.")
Signed-off-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210915100507.3945-1-itoral@igalia.com

drivers/gpu/drm/v3d/v3d_gem.c

@@ -197,8 +197,8 @@ v3d_clean_caches(struct v3d_dev *v3d)
 
 	V3D_CORE_WRITE(core, V3D_CTL_L2TCACTL, V3D_L2TCACTL_TMUWCF);
 	if (wait_for(!(V3D_CORE_READ(core, V3D_CTL_L2TCACTL) &
-		       V3D_L2TCACTL_L2TFLS), 100)) {
-		DRM_ERROR("Timeout waiting for L1T write combiner flush\n");
+		       V3D_L2TCACTL_TMUWCF), 100)) {
+		DRM_ERROR("Timeout waiting for TMU write combiner flush\n");
 	}
 
 	mutex_lock(&v3d->cache_clean_lock);