staging: vchiq_core: Fix missing semaphore release in error case

The bail out branch in case of a invalid tx_pos missed a semaphore
release. Dan Carpenter found this with a static checker.

Fixes: d1eab9de ("staging: vchiq_core: Bail out in case of invalid tx_pos")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c

@@ -601,6 +601,7 @@ reserve_space(VCHIQ_STATE_T *state, size_t space, int is_blocking)
 		}
 
 		if (tx_pos == (state->slot_queue_available * VCHIQ_SLOT_SIZE)) {
+			up(&state->slot_available_event);
 			pr_warn("%s: invalid tx_pos: %d\n", __func__, tx_pos);
 			return NULL;
 		}