OMAPFB: remove mem info from platform_data

omapfb driver used platform_data to get fb memory areas and formats
defined by the board file.

This patch removes omapfb's (both old and new omapfb) use of the
memory data in platform_data, because:

- No board uses them currently
- It's not board file's job to define things like amount of default
  framebuffer memory. These should come from the bootloader via command
  line parameters.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>