drivers: ssd1306: Add SPI support

This change allows to use SSD1306 based displays to be used on the
SPI bus as well.
Adding SPI shield.
Tested on SSD1306 and SSD1309 based displays using I2C.
Tested on SSD1309 based display using SPI.

Signed-off-by: Marco Peter <marco@peter-net.ch>
8 files changed