KVM: Document KVM_SET_SIGNAL_MASK as universal

KVM_SET_SIGNAL_MASK is implemented in generic code and isn't x86
specific, so document it as being applicable for all architectures.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: kvm@vger.kernel.org
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: linux-doc@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Documentation/virtual/kvm/api.txt

@@ -512,7 +512,7 @@ struct kvm_cpuid {
 4.21 KVM_SET_SIGNAL_MASK
 
 Capability: basic
-Architectures: x86
+Architectures: all
 Type: vcpu ioctl
 Parameters: struct kvm_signal_mask (in)
 Returns: 0 on success, -1 on error