ARM: PRIMA2: irq: make prima2 irq can work even we enable GIC for Marco

in Marco, we will use GIC. this patch prepares the handle_irq for prima2
to avoid the compiling errors since we want only one defconfig and zImage
for both prima2 and marco that means we will need handle_irq for both.

Signed-off-by: Baohua Song <Baohua.Song@csr.com>