ARM: OMAP2+: irq, AM33XX add missing register check

am33xx has a INTC_PENDING_IRQ3 register that is not checked for pending
interrupts. This patch adds AM33XX to the ifdef of SOCs that have to
check this register.

Cc: stable@vger.kernel.org
Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Tony Lindgren <tony@atomide.com>