drm/amd/display: fix spelling mistake "exeuction" -> "execution"

There are spelling mistakes in a DC_ERROR message and a comment.
Fix these.

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dmub/inc/dmub_srv.h

@@ -416,7 +416,7 @@ enum dmub_status dmub_srv_cmd_queue(struct dmub_srv *dmub,
  * dmub_srv_cmd_execute() - Executes a queued sequence to the dmub
  * @dmub: the dmub service
  *
- * Begins exeuction of queued commands on the dmub.
+ * Begins execution of queued commands on the dmub.
  *
  * Return:
  *   DMUB_STATUS_OK - success