hw/intc/arm_gic: Add grouping support to gic_update()

Add support to gic_update() for determining the current IRQ
and FIQ status when interrupt grouping is supported. This
simply requires that instead of always raising IRQ we
check the group of the highest priority pending interrupt
and the GICC_CTLR.FIQEn bit to see whether we should raise
IRQ or FIQ.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-id: 1430502643-25909-15-git-send-email-peter.maydell@linaro.org
