KVM: arm64: Remove pointless check for changed init target

At any time there is only a single valid value for KVM_ARM_VCPU_INIT,
depending on the current CPU implementation. In all likelihood, this
will be the generic ARMv8 target.

Drop the pointless check for a changed target value between calls to
KVM_ARM_VCPU_INIT and instead rely on the check against
kvm_target_cpu().

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230710193140.1706399-3-oliver.upton@linux.dev