treewide: remove DRIVER_11N_SUPPORT

hostapd's compile time option CONFIG_IEEE80211N was removed almost 3 years
ago, 80.211n/HT is always included since then.

Noticed because `hostapd -v11n` confusingly returned an error.

See hostapd's commit:
f3bcd69603 "Remove CONFIG_IEEE80211N build option"

Signed-off-by: Andre Heider <a.heider@gmail.com>

package/network/services/hostapd/Config.in

@@ -68,10 +68,6 @@ config DRIVER_WEXT_SUPPORT
 	select KERNEL_WIRELESS_EXT
 	default n
 
-config DRIVER_11N_SUPPORT
-	bool
-	default n
-
 config DRIVER_11AC_SUPPORT
 	bool
 	default n

package/network/services/hostapd/Makefile

@@ -28,7 +28,6 @@ PKG_CONFIG_DEPENDS:= \
 	CONFIG_PACKAGE_hostapd-mini \
 	CONFIG_WPA_RFKILL_SUPPORT \
 	CONFIG_DRIVER_WEXT_SUPPORT \
-	CONFIG_DRIVER_11N_SUPPORT \
 	CONFIG_DRIVER_11AC_SUPPORT \
 	CONFIG_DRIVER_11AX_SUPPORT \
 	CONFIG_WPA_ENABLE_WEP
@@ -71,11 +70,6 @@ include $(INCLUDE_DIR)/package.mk
 
 STAMP_CONFIGURED:=$(STAMP_CONFIGURED)_$(CONFIG_WPA_MSG_MIN_PRIORITY)
 
-
-ifneq ($(CONFIG_DRIVER_11N_SUPPORT),)
-  HOSTAPD_IEEE80211N:=y
-endif
-
 ifneq ($(CONFIG_DRIVER_11AC_SUPPORT),)
   HOSTAPD_IEEE80211AC:=y
 endif
@@ -87,7 +81,6 @@ endif
 DRIVER_MAKEOPTS= \
 	CONFIG_ACS=$(CONFIG_PACKAGE_kmod-cfg80211) \
 	CONFIG_DRIVER_NL80211=$(CONFIG_PACKAGE_kmod-cfg80211) \
-	CONFIG_IEEE80211N=$(HOSTAPD_IEEE80211N) \
 	CONFIG_IEEE80211AC=$(HOSTAPD_IEEE80211AC) \
 	CONFIG_IEEE80211AX=$(HOSTAPD_IEEE80211AX) \
 	CONFIG_DRIVER_WEXT=$(CONFIG_DRIVER_WEXT_SUPPORT) \

package/network/services/hostapd/src/src/utils/build_features.h

@@ -7,10 +7,6 @@ static inline int has_feature(const char *feat)
 	if (!strcmp(feat, "eap"))
 		return 1;
 #endif
-#ifdef CONFIG_IEEE80211N
-	if (!strcmp(feat, "11n"))
-		return 1;
-#endif
 #ifdef CONFIG_IEEE80211AC
 	if (!strcmp(feat, "11ac"))
 		return 1;