staging: rtl8821ae: fix sparse warning for static declarations in rtl8821ae/stats.c

This patch fixes the following sparse warnings in rtl8821ae/stats.c

drivers/staging/rtl8821ae/stats.c:62:6: warning: symbol 'rtl_translate_todbm' was not declared. Should it be static?
drivers/staging/rtl8821ae/stats.c:101:6: warning: symbol 'rtl_process_ui_rssi' was not declared. Should it be static?

Signed-off-by: Hoang Tran <hoangtran.gwr@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>