KVM: arm64: nv: Add trap description for SPSR_EL2 and ELR_EL2

Having carved a hole for SP_EL1, we are now missing the entries
for SPSR_EL2 and ELR_EL2. Add them back.

Reported-by: Miguel Luis <miguel.luis@oracle.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>