DMA: PL330: Fix potential NULL pointer dereference in pl330_submit_req()

commit 2e2c682becb20416c140aa0d6d3137b51a5c76da upstream.

'r->cfg' is being checked for NULL. However, it is dereferenced
in the previous statements. Thus moving those statements within
the check.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Acked-by: Jassi Brar <jassisinghbrar@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>