MIPS: traps: Fix output of show_backtrace

Since commit 4bcc595c ("printk: reinstate KERN_CONT for printing
continuation lines") the output from show_backtrace on MIPS has been
pretty unreadable due to the lack of KERN_CONT markers. Use pr_cont to
provide the appropriate markers & restore the expected output.
Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: Maciej W. Rozycki <macro@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14429/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/traps.c

@@ -156,7 +156,7 @@ static void show_backtrace(struct task_struct *task, const struct pt_regs *regs)
 		print_ip_sym(pc);
 		pc = unwind_stack(task, &sp, pc, &ra);
 	} while (pc);
-	printk("\n");
+	pr_cont("\n");
 }
 
 /*