KVM: x86 emulator: Make x86_decode_insn() return proper macros

Return EMULATION_OK/FAILED consistently.  Also treat instruction fetch
errors, not restricted to X86EMUL_UNHANDLEABLE, as EMULATION_FAILED;
although this cannot happen in practice, the current logic will continue
the emulation even if the decoder fails to fetch the instruction.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d28dff7..1fe9637 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4837,7 +4837,7 @@
 
 		trace_kvm_emulate_insn_start(vcpu);
 		++vcpu->stat.insn_emulation;
-		if (r)  {
+		if (r != EMULATION_OK)  {
 			if (emulation_type & EMULTYPE_TRAP_UD)
 				return EMULATE_FAIL;
 			if (reexecute_instruction(vcpu, cr2))