ARM: h1940: Fix backlight and LCD power functions

Current implementation of LCD and backlight power control functions
is not complete, as result PDA consumes power in suspend.
Fix this issue by managing state of some latch bits, just like
WinMobile does.

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>