evdev: Add LED update hook
evdev: Add LED update hook

Simply pushes the updated LEDs through to all keyboard attached to the
seat.

Signed-off-by: Daniel Stone <3d0f3b9ddcacec30c4008c5e030e6c13a478cb4f@fooishbar.org>

xorgy/weston,jonnylamb/weston,eyolfson/weston,giucam/weston,krezovic/weston,jonnylamb/weston,eyolfson/weston,Gnurou/weston,Tarnyko/weston-xdg_surface_present,Fantu/compositor-spice,Fantu/compositor-spice,mchalupa/weston,udoprog/weston,kwm81/weston,krezovic/weston,Fantu/compositor-spice,Gnurou/weston,Tarnyko/weston-xdg_surface_present,kwm81/weston,giucam/weston,sir-murray/weston,udoprog/weston,mchalupa/weston,sir-murray/weston,xorgy/weston