KVM: arm/arm64: fix the incompatible matching for external abort

kvm_vcpu_dabt_isextabt() tries to match a full fault syndrome, but
calls kvm_vcpu_trap_get_fault_type() that only returns the fault class,
thus reducing the scope of the check. This doesn't cause any observable
bug yet as we end-up matching a closely related syndrome for which we
return the same value.

Using kvm_vcpu_trap_get_fault() instead fixes it for good.

Signed-off-by: Dongjiu Geng <gengdongjiu@huawei.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>