mfd: rtsx: Add support for card reader rtl8402

rtl8402 is much like rtl8411, so just add it to rtl8411.c

Signed-off-by: Micky Ching <micky_ching@realsil.com.cn>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>