hw/arm_gic: Fix comparison with priority mask register

hw/arm_gic: Fix comparison with priority mask register

The GIC spec states that only interrupts with higher priority
than the value in the GICC_PMR priority mask register are
passed through to the processor. We were incorrectly allowing
through interrupts with a priority equal to the specified
value: correct the comparison operation to match the spec.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Igor Mitsyanko <i.mitsyanko@samsung.com>