powerpc: Export kvm_guest static key, for bcachefs six locks

bcachefs's six locks need kvm_guest, via
 ower_on_cpu() ->  vcpu_is_preempted() -> is_kvm_guest()

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Cc: linuxppc-dev@lists.ozlabs.org
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

arch/powerpc/kernel/firmware.c

@@ -23,6 +23,8 @@ EXPORT_SYMBOL_GPL(powerpc_firmware_features);
 
 #if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_KVM_GUEST)
 DEFINE_STATIC_KEY_FALSE(kvm_guest);
+EXPORT_SYMBOL_GPL(kvm_guest);
+
 int __init check_kvm_guest(void)
 {
 	struct device_node *hyper_node;