arm64: Make do_bad_area() function static

This function is only called from arch/arm64/mm/fault.c.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/mm/fault.c

@@ -130,7 +130,7 @@ static void __do_user_fault(struct task_struct *tsk, unsigned long addr,
 	force_sig_info(sig, &si, tsk);
 }
 
-void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs)
+static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs)
 {
 	struct task_struct *tsk = current;
 	struct mm_struct *mm = tsk->active_mm;