powerpc: Fix single step emulation of 32bit overflowed branches

Check truncate_if_32bit() on final write to nip.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/lib/sstep.c

@@ -580,7 +580,7 @@ int __kprobes emulate_step(struct pt_regs *regs, unsigned int instr)
 		if (instr & 1)
 			regs->link = regs->nip;
 		if (branch_taken(instr, regs))
-			regs->nip = imm;
+			regs->nip = truncate_if_32bit(regs->msr, imm);
 		return 1;
 #ifdef CONFIG_PPC64
 	case 17:	/* sc */