ARM: VGIC: rename gic_event_needs_delivery()

ARM: VGIC: rename gic_event_needs_delivery()

gic_event_needs_delivery() is not named very intuitively, especially
the gic_ prefix is somewhat misleading.
Rename it to vgic_vcpu_pending_irq(), which makes it clear that this
relates to the virtual GIC and is about interrupts.
Also add a VCPU parameter, which makes the code more flexible in the
future. The current VGIC expect this to be the current VCPU, so add
an assert to spot any regressions.

Signed-off-by: Andre Przywara <andre.przywara@linaro.org>
Reviewed-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>