ARM: mxc: fix local timer interrupt handling

As local timer interrupts are now handled as normal interrupts,
remove the special case in the GIC handler.

Cc: Shawn Guo <shawn.guo@linaro.org>
Cc: Sascha Hauer <kernel@pengutronix.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Tested-and-Acked-by: Shawn Guo <shawn.guo@linaro.org>