package/rtl8723bu: fix build failure due to missing Linux options

This driver requires:
CONFIG_NET
CONFIG_WIRELESS
CONFIG_CFG80211
CONFIG_USB_SUPPORT
CONFIG_USB
to build so let's add them to RTL8723BU_LINUX_CONFIG_FIXUPS.

Fixes:
http://autobuild.buildroot.net/results/7f3637760ad88d314e6812865f3667d1de091957/

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 1978e9b0219712b2b839d9f44a0b98b2e8280f75)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/rtl8723bu/rtl8723bu.mk

@@ -12,6 +12,14 @@ RTL8723BU_MODULE_MAKE_OPTS = \
 	KVER=$(LINUX_VERSION_PROBED) \
 	KSRC=$(LINUX_DIR)
 
+define RTL8723BU_LINUX_CONFIG_FIXUPS
+	$(call KCONFIG_ENABLE_OPT,CONFIG_NET)
+	$(call KCONFIG_ENABLE_OPT,CONFIG_WIRELESS)
+	$(call KCONFIG_ENABLE_OPT,CONFIG_CFG80211)
+	$(call KCONFIG_ENABLE_OPT,CONFIG_USB_SUPPORT)
+	$(call KCONFIG_ENABLE_OPT,CONFIG_USB)
+endef
+
 define RTL8723BU_INSTALL_TARGET_CMDS
 	$(INSTALL) -D -m 644 $(@D)/rtl8723b_fw.bin $(TARGET_DIR)/lib/firmware/rtl_bt/rtl8723b_fw.bin
 endef