mx51: support FIQ on TZIC, revised

Add support for FIQ on mx51 TZIC

TZIC changes tested with FIQ audio on an mx51 board

AVIC changes build with mx3_defconfig, not tested

Signed-off-by: Peter Horton <phorton@bitbox.co.uk>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>