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>