keymap: Only run on key devices

Skip event devices which don't have ID_INPUT_KEY set, to avoid running the long
list of rules more than necessary.

Note that we don't limit ourselves to ID_INPUT_KEYBOARD, as we might want to
fix extra buttons on e. g. fancy mouses or tablet screens, too.

extras/keymap/95-keymap.rules

@@ -6,8 +6,8 @@
 # pairs.
 
 ACTION=="remove", GOTO="keyboard_end"
-SUBSYSTEM!="input", GOTO="keyboard_end"
 KERNEL!="event*", GOTO="keyboard_end"
+ENV{ID_INPUT_KEY}=="", GOTO="keyboard_end"
 SUBSYSTEMS=="bluetooth", GOTO="keyboard_end"
 
 SUBSYSTEMS=="usb", ENV{ID_VENDOR}=="", IMPORT{program}="usb_id --export %p"