bcm4908: add kmod-gpio-button-hotplug

All bcm4908 devices are expected to have GPIO buttons to make relevant
package selected by default.
This "fixes" triggering failsafe mode.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

target/linux/bcm4908/Makefile

@@ -22,6 +22,7 @@ KERNELNAME:=Image dtbs
 
 DEFAULT_PACKAGES += \
 	bcm4908img \
+	kmod-gpio-button-hotplug \
 	kmod-usb-ohci kmod-usb2 kmod-usb3
 
 $(eval $(call BuildTarget))