KVM: arm64: nv: Support virtual EL2 exceptions

KVM: arm64: nv: Support virtual EL2 exceptions

Support injecting exceptions and performing exception returns to and
from virtual EL2.  This must be done entirely in software except when
taking an exception from vEL0 to vEL2 when the virtual HCR_EL2.{E2H,TGE}
== {1,1}  (a VHE guest hypervisor).

[maz: switch to common exception injection framework, illegal exeption
 return handling]

Reviewed-by: Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>
Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230209175820.1939006-10-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>