staging: rtl8188eu: remove the "trigger gpio 0" hal variable

The hal variable to trigger gpio 0 seems to be a leftover from debugging
code that was removed. An empty function is called when this variable is
written to.

Remove the empty function and the variable itself. It should be safe to
remove an entry from the hw_variables enum as this enum is used only
within the rtl8188eu driver.
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20210718173610.894-2-martin@kaiser.cxSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8188eu/hal/usb_halinit.c

@@ -1002,11 +1002,6 @@ void rtw_hal_read_chip_info(struct adapter *Adapter)
 	readAdapterInfo_8188EU(Adapter);
 }
 
-#define GPIO_DEBUG_PORT_NUM 0
-static void rtl8192cu_trigger_gpio_0(struct adapter *adapt)
-{
-}
-
 static void ResumeTxBeacon(struct adapter *adapt)
 {
 	struct hal_data_8188e *haldata = adapt->HalData;
@@ -1550,9 +1545,6 @@ void rtw_hal_set_hwreg(struct adapter *Adapter, u8 variable, u8 *val)
 			}
 		}
 		break;
-	case HW_VAR_TRIGGER_GPIO_0:
-		rtl8192cu_trigger_gpio_0(Adapter);
-		break;
 	case HW_VAR_RPT_TIMER_SETTING:
 		{
 			u16 min_rpt_time = (*(u16 *)val);

drivers/staging/rtl8188eu/include/hal_intf.h

@@ -74,7 +74,6 @@ enum hw_variables {
 	HW_VAR_TDLS_RS_RCR,
 	HW_VAR_TDLS_DONE_CH_SEN,
 	HW_VAR_INITIAL_GAIN,
-	HW_VAR_TRIGGER_GPIO_0,
 	HW_VAR_BT_SET_COEXIST,
 	HW_VAR_BT_ISSUE_DELBA,
 	HW_VAR_CURRENT_ANTENNA,