We don't need to mess with CCU_IO register (it's only needed for targets
with a SD slot) so don't keep its value when changing buttonlight
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@19139 a1c6a512-1295-4272-9138-f99709370657
Revive lcd_enable() as well, and use it in _backlight_on/off()
Don't update the lcd framebuffer if the display is off
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@18952 a1c6a512-1295-4272-9138-f99709370657