tegra: Add SOC support for display/lcd

Add support for the LCD peripheral at the Tegra2 SOC level. A separate
LCD driver will use this functionality to configure the display.

Signed-off-by: Mayuresh Kulkarni <mkulkarni@nvidia.com>
Mayuresh Kulkarni:
- changes to remove bitfields and clean up for submission

Signed-off-by: Simon Glass <sjg@chromium.org>
Simon Glass:
- simplify code, move clock control into here, clean-up
Signed-off-by: Tom Warren <twarren@nvidia.com>