Fixes:

build_dir/target-arm_cortex-a9+vfpv3-d16_musl_eabi/linux-mvebu_cortexa9/gpio-button-hotplug/gpio-button-hotplug.c:193:2: error: implicit declaration of function 'broadcast_uevent'; did you mean 'kobject_uevent'? [-Werror=implicit-function-declaration]
  broadcast_uevent(event->skb, 0, 1, GFP_KERNEL);
  ^~~~~~~~~~~~~~~~
  kobject_uevent
cc1: some warnings being treated as errors

This patch can be removed as it is, because this patch is in OpenWrt
repository and only for kernel 5.4, so revert does not work when the
patch is not there