video: ssd1307fb: Rework the communication functions

To efficiently send a whole page to the display, we need to be able to
manipulate more easily the data arrays that has to be sent to the OLED
controller. As such, this patch introduces a ssd1307fb_array structure
that handles both the small header to be sent over i2c, which contains
the type of information sent, and the raw bytes after that.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>