KVM: arm64: Add predicate for FPMR support in a VM

As we are about to check for the advertisement of FPMR support to
a guest in a number of places, add a predicate that will gate most
of the support code for FPMR.

Reviewed-by: Mark Brown <broonie@kernel.org>
Tested-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20240820131802.3547589-3-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/include/asm/kvm_host.h

@@ -1475,4 +1475,8 @@ void kvm_set_vm_id_reg(struct kvm *kvm, u32 reg, u64 val);
 		(pa + pi + pa3) == 1;					\
 	})
 
+#define kvm_has_fpmr(k)					\
+	(system_supports_fpmr() &&			\
+	 kvm_has_feat((k), ID_AA64PFR2_EL1, FPMR, IMP))
+
 #endif /* __ARM64_KVM_HOST_H__ */