Staging: fbtft: Use a struct to describe each LCD controller

Use a struct flexfb_lcd_controller to holds chip properties, instead of
relying on a long 'if - else if' chain.
This allows to:
- use a simple linear search to verify if a certain LCD controller
model is supported or not.
- add support for a new LCD chip controller simply defining a new
flexfb_lcd_controller struct.

Signed-off-by: Fabio Falzoi <fabio.falzoi84@gmail.com>
Acked-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>