ARM: S3C2410: H1940: Fix lcd_power_set function

Current implementation of lcd_power_set is not reliable, sometimes
it does not enable LCD at all.
Mimic WinCE behavior to fix this issue.

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