staging: r8188eu: Make rtw_signal_stat_timer_hdl a static function

Make rtw_signal_stat_timer_hdl a static function instead of a global
function.

Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Signed-off-by: Chang Yu <marcus.yu.56@gmail.com>
Link: https://lore.kernel.org/r/20220623043855.407208-1-marcus.yu.56@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/r8188eu/core/rtw_recv.c

@@ -24,7 +24,7 @@ static u8 rtw_rfc1042_header[] = {
 	0xaa, 0xaa, 0x03, 0x00, 0x00, 0x00
 };
 
-void rtw_signal_stat_timer_hdl(struct timer_list *t);
+static void rtw_signal_stat_timer_hdl(struct timer_list *t);
 
 void _rtw_init_sta_recv_priv(struct sta_recv_priv *psta_recvpriv)
 {
@@ -1794,7 +1794,7 @@ s32 rtw_recv_entry(struct recv_frame *precvframe)
 	return ret;
 }
 
-void rtw_signal_stat_timer_hdl(struct timer_list *t)
+static void rtw_signal_stat_timer_hdl(struct timer_list *t)
 {
 	struct adapter *adapter = from_timer(adapter, t, recvpriv.signal_stat_timer);
 	struct recv_priv *recvpriv = &adapter->recvpriv;