MIPS: rtlx: Fix implicit declaration of function set_vi_handler()

arch/mips/kernel/rtlx.c: In function 'rtlx_module_init':
arch/mips/kernel/rtlx.c:523:3: error: implicit declaration of function 'set_vi_handler' [-Werror=implicit-function-declaration]

Signed-off-by: Yoichi Yuasa <yuasa@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5340/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>