user-exec-stub: remove unused variable

enable_cpu_pm is only used by softmmu-specific code, namely target/i386/host-cpu.c
and target/i386/kvm/*.  It does not need a stub definition anymore.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/accel/tcg/user-exec-stub.c b/accel/tcg/user-exec-stub.c
index 874e1f1..2dc6fd9 100644
--- a/accel/tcg/user-exec-stub.c
+++ b/accel/tcg/user-exec-stub.c
@@ -2,8 +2,6 @@
 #include "hw/core/cpu.h"
 #include "exec/replay-core.h"
 
-bool enable_cpu_pm = false;
-
 void cpu_resume(CPUState *cpu)
 {
 }