KVM: nVMX: Replace a BUG_ON(1) with BUG() to squash clang warning

Use BUG() in the impossible-to-hit default case when switching on the
scope of INVEPT to squash a warning with clang 11 due to clang treating
the BUG_ON() as conditional.

  >> arch/x86/kvm/vmx/nested.c:5246:3: warning: variable 'roots_to_free'
     is used uninitialized whenever 'if' condition is false
     [-Wsometimes-uninitialized]
                   BUG_ON(1);

Reported-by: kbuild test robot <[email protected]>
Fixes: ce8fe7b ("KVM: nVMX: Free only the affected contexts when emulating INVEPT")
Signed-off-by: Sean Christopherson <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

Author: Sean Christopherson

arch/x86/kvm/vmx/nested.c

@@ -5165,7 +5165,7 @@ static int handle_invept(struct kvm_vcpu *vcpu)
 	 */
 		break;
 	default:
-		BUG_ON(1);
+		BUG();
 		break;
 	}