drm/vmwgfx: Restart command buffers after errors

Previously we skipped the command buffer and added an extra fence to
avoid hangs due to skipped fence commands.
Now we instead restart the command buffer after the failing command,
if there are any commands left.
In addition we print out some information about the failing command
and its location in the command buffer.

Testing Done: ran glxgears using mesa modified to send the NOP_ERROR
command before each 10th clear and verified that we detected the device
error properly and that there were no other device errors caused by
incorrectly ordered command buffers. Also ran the piglit "quick" test
suite which generates a couple of device errors and verified that
they were handled as intended.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>

drivers/gpu/drm/vmwgfx/vmwgfx_drv.h

@@ -846,7 +846,7 @@ extern int vmw_validate_single_buffer(struct vmw_private *dev_priv,
 				      struct ttm_buffer_object *bo,
 				      bool interruptible,
 				      bool validate_as_mob);
-
+bool vmw_cmd_describe(const void *buf, u32 *size, char const **cmd);
 
 /**
  * IRQs and wating - vmwgfx_irq.c