arch-arm: Fix Virtual interrupts in AArch64

arch-arm: Fix Virtual interrupts in AArch64

Checking if cpsr.mode is equal to MODE_HYP doesn't work for AArch64.
This is because AArch64 is using different modes when in EL2, like EL2T
and EL2H.
This made Virtual Interrupts to be triggered even when executing in EL2
(hypervisor) whereas they should interrupt the scheduled VM only
(Non-Secure EL0 and EL1). This patch is fixing this by using the generic
currEL() helper for getting the exception level, which is working for
both AArch32 and AArch64.

Change-Id: I08640050ef06261f280ba1e63ca9f32c805af845
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/16202
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>