x86: single_step 0xf0

This fixes the 64-bit single-step handling code's instruction
decoder to grok the 0xf0 (lock) prefix, which the 32-bit code
already does correctly.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/step.c

@@ -66,7 +66,7 @@ static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
 		case 0x26: case 0x2e:
 		case 0x36: case 0x3e:
 		case 0x64: case 0x65:
-		case 0xf2: case 0xf3:
+		case 0xf0: case 0xf2: case 0xf3:
 			continue;
 
 		case 0x40 ... 0x4f: