ARC: Fix -Wmissing-prototypes warnings

ARC: Fix -Wmissing-prototypes warnings

| ../arch/arc/kernel/kprobes.c:193:15: warning: no previous prototype for 'arc_kprobe_handler' [-Wmissing-prototypes]
|  193 | int __kprobes arc_kprobe_handler(unsigned long addr, struct pt_regs *regs)
|
|../arch/arc/kernel/ptrace.c:342:16: warning: no previous prototype for 'syscall_trace_enter' [-Wmissing-prototypes]
|  342 | asmlinkage int syscall_trace_enter(struct pt_regs *regs)

Link: https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20240325/testrun/23149630/suite/build/test/gcc-9-defconfig/log
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Signed-off-by: Vineet Gupta <vgupta@kernel.org>