MIPS: KVM: Convert EXPORT_SYMBOL to _GPL

Export symbols only to GPL modules to match other KVM symbols in
virt/kvm/ and arch/*/kvm/.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/11887/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kvm/callback.c

@@ -11,4 +11,4 @@
 #include <linux/kvm_host.h>
 
 struct kvm_mips_callbacks *kvm_mips_callbacks;
-EXPORT_SYMBOL(kvm_mips_callbacks);
+EXPORT_SYMBOL_GPL(kvm_mips_callbacks);