KVM: arm64: BUG on failure to drop host privileges

In pKVM mode we should never fail to drop host privileges but, if
we do, we could be in an inconsistent state:
1. static key is flipped but we haven't completed initialisation
2. only a subset of CPUs may have dropped host privileges

In this scenario, BUG is the only sensible action.

Signed-off-by: Keir Fraser <keirf@google.com>

arch/arm64/kvm/pkvm.c

diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c
index 9b52ca9..d69f784 100644
--- a/arch/arm64/kvm/pkvm.c
+++ b/arch/arm64/kvm/pkvm.c
@@ -334,10 +334,10 @@ static int __init finalize_pkvm(void)
 	ret = pkvm_drop_host_privileges();
 	if (ret) {
 		pr_err("Failed to finalize Hyp protection: %d\n", ret);
-		pkvm_firmware_rmem_clear();
+		BUG();
 	}
 
-	return ret;
+	return 0;
 }
 device_initcall_sync(finalize_pkvm);