OMAPDSS: panels: keep platform data of all panels in a single header

Structs for platform data of omapdss panels are found in headers in the
'include/video/' path. Board files populate these structs with platform
specific values, and the panel driver uses these to configure the panel.

Currently, each panel has it's own header in the above path. Move all the
omapdss panel platform data structs to a single header omap-panel-data.h.
This is useful because:

- All other omapdss panel drivers will be modified to use platform data. This
  would lead to a lot of panel headers usable only by omapdss. A lot of these
  platform data structs are trivial, and don't really need a separate header.
- Platform data would be eventually removed, and platform information would be
  passed via device tree. Therefore, omapdss panel platform data structs are
  temporary, and will be easier to remove if they are all in the same header.
- All board files will have to include the same header to configure a panel's
  platform data, that makes the board files more consistent.

Signed-off-by: Archit Taneja <archit@ti.com>