qemu: Fix interrupt type check

Function plat_ic_get_pending_interrupt_type() should return interrupt
type, not id. The function is used in aarch64 exception handling and
currently the irq/fiq forwarding fails if a secure interrupt happens while
running normal world.

The qemu-specific gic file does not contain any extra functionality so it
can be removed and common file can be used instead.

fixes arm-software/tf-issues#546

Signed-off-by: Santeri Salko <santeri.salko@gmail.com>