staging: rtl8723bs: core: remove set but not used 'pframe'

Fix the following gcc warning:

drivers/staging/rtl8723bs/core/rtw_mlme.c:2920:6: warning: variable
‘pframe’ set but not used [-Wunused-but-set-variable]
  u8 *pframe;
      ^~~~~~
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Link: https://lore.kernel.org/r/20200427032342.27211-8-yanaijie@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8723bs/core/rtw_mlme.c

@@ -2914,12 +2914,11 @@ void rtw_append_exented_cap(struct adapter *padapter, u8 *out_ie, uint *pout_len
 	struct mlme_priv *pmlmepriv = &padapter->mlmepriv;
 	struct ht_priv 	*phtpriv = &pmlmepriv->htpriv;
 	u8 cap_content[8] = {0};
-	u8 *pframe;
 
 	if (phtpriv->bss_coexist)
 		SET_EXT_CAPABILITY_ELE_BSS_COEXIST(cap_content, 1);
 
-	pframe = rtw_set_ie(out_ie + *pout_len, EID_EXTCapability, 8, cap_content, pout_len);
+	rtw_set_ie(out_ie + *pout_len, EID_EXTCapability, 8, cap_content, pout_len);
 }
 
 inline void rtw_set_to_roam(struct adapter *adapter, u8 to_roam)