KVM: arm64: Allow kvm_has_feat() to take variable arguments

In order to be able to write more compact (and easier to read) code,
let kvm_has_feat() and co take variable arguments. This enables
constructs such as:

	#define FEAT_SME	ID_AA64PFR1_EL1, SME, IMP

	if (kvm_has_feat(kvm, FEAT_SME))
		[...]

which is admitedly more readable.

Signed-off-by: Marc Zyngier <maz@kernel.org>