powerpc/traps: Fix the message printed when stack overflows

Today's message is useless:

  [   42.253267] Kernel stack overflow in process (ptrval), r1=c65500b0

This patch fixes it:

  [   66.905235] Kernel stack overflow in process sh[356], r1=c65560b0

Fixes: ad67b74d ("printk: hash addresses printed with %p")
Cc: stable@vger.kernel.org # v4.15+
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
[mpe: Use task_pid_nr()]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/traps.c

@@ -1535,8 +1535,8 @@ void alignment_exception(struct pt_regs *regs)
 
 void StackOverflow(struct pt_regs *regs)
 {
-	printk(KERN_CRIT "Kernel stack overflow in process %p, r1=%lx\n",
-	       current, regs->gpr[1]);
+	pr_crit("Kernel stack overflow in process %s[%d], r1=%lx\n",
+		current->comm, task_pid_nr(current), regs->gpr[1]);
 	debugger(regs);
 	show_regs(regs);
 	panic("kernel stack overflow");