mfd: rtsx: Fix sparse non static symbol warning

Fixes the following sparse warning:

drivers/mfd/rtl8411.c:473:6: warning:
 symbol 'rtl8411_init_common_params' was not declared. Should it be static?

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Lee Jones <lee.jones@linaro.org>