staging: greybus: loopback_test: Add blank line after declaration.

Declarations are to be followed by a blank line. Add to follow Linux
Kernel coding style. Issue reported by checkpatch.
Reviewed-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Jack Schofield <schofija@oregonstate.edu>
Link: https://lore.kernel.org/r/048967b5c3b157e19ccf4608f71da8418fc31877.1669872193.git.schofija@oregonstate.eduSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/greybus/tools/loopback_test.c

@@ -675,6 +675,7 @@ static int open_poll_files(struct loopback_test *t)
 static int close_poll_files(struct loopback_test *t)
 {
 	int i;
+
 	for (i = 0; i < t->poll_count; i++)
 		close(t->fds[i].fd);