staging: greybus: loopback: fix a spelling error.

asynchronus -> asynchronous
Signed-off-by: Steve Lemuel <wlemuel@hotmail.com>
Link: https://lore.kernel.org/r/SYBP282MB347864E247D2EC70BF46F9A3A0A29@SYBP282MB3478.AUSP282.PROD.OUTLOOK.COMSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/greybus/loopback.c

@@ -870,7 +870,7 @@ static int gb_loopback_fn(void *data)
 		if (gb->send_count == gb->iteration_max) {
 			mutex_unlock(&gb->mutex);
 
-			/* Wait for synchronous and asynchronus completion */
+			/* Wait for synchronous and asynchronous completion */
 			gb_loopback_async_wait_all(gb);
 
 			/* Mark complete unless user-space has poked us */