New LLD: HVGA_X81
For HVGA : 320 x 480, 16bpp displays,
controlled by ILI9481 or compatible controllers.

* Pixel readback TODO
* Powermodes: Sleep implemented
Renamed HVGA_X81 to ILI9481
Merge pull request #66 from abhishek-kakkar/master

New LLD: ILI9481