Drop the useless NULL check on kvm_x86_ops.check_apicv_inhibit_reasons
when handling an APICv update, both VMX and SVM unconditionally implement
the helper and leave it non-NULL even if APICv is disabled at the module
level.  The latter is a moot point now that __kvm_request_apicv_update()
is called if and only if enable_apicv is true.

No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211208015236.1616697-26-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>