ARM: 7326/2: PL330: fix null pointer dereference in pl330_chan_ctrl()

This fixes the thrd->req_running field being accessed before thrd
is checked for null. The error was introduced in

   abb959f8: ARM: 7237/1: PL330: Fix driver freeze

Reference: <1326458191-23492-1-git-send-email-mans.rullgard@linaro.org>

Cc: stable@kernel.org
Signed-off-by: Mans Rullgard <mans.rullgard@linaro.org>
Acked-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/common/pl330.c

@@ -1502,12 +1502,13 @@ int pl330_chan_ctrl(void *ch_id, enum pl330_chan_op op)
 	struct pl330_thread *thrd = ch_id;
 	struct pl330_dmac *pl330;
 	unsigned long flags;
-	int ret = 0, active = thrd->req_running;
+	int ret = 0, active;
 
 	if (!thrd || thrd->free || thrd->dmac->state == DYING)
 		return -EINVAL;
 
 	pl330 = thrd->dmac;
+	active = thrd->req_running;
 
 	spin_lock_irqsave(&pl330->lock, flags);