KVM: arm64: Check for SYSREGS_ON_CPU before accessing the 32bit state

Just like c6e35dff ("KVM: arm64: Check for SYSREGS_ON_CPU before
accessing the CPU state") fixed the 64bit state access, add a check
for the 32bit state actually being on the CPU before writing it.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250817121926.217900-2-maz@kernel.org


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>