gpio-button-hotplug: fix active_low handling, possibly broken in r37643

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37664 3c298f89-4303-0410-b956-a3cf2f4a3e73
gpio-button-hotplug: cleanup, fix compiler warning

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37665 3c298f89-4303-0410-b956-a3cf2f4a3e73