drivers: staging: fbtft: Fix fb_ssd1306 driver for 128x32 Display

[pawel-soja]

The driver incorrectly sets the column and page addresses for a 128x32 display.
Display used is from the Environmental Sensor Board kit.
The final values ​​of the addresses should be:

• 0x7F for cols because it is 128 - 1
• 0x03 for rows because it is 32 / 8 (bits, vertical addressing) - 1

Before:

After:

[6by9]

Slight dilemma here in that fbtft is orphaned and considered deprecated by upstream. DRM drivers (mainly mipi-dbi-spi) should be used instead.

However we do have 2 downstream patches to fbtft already, so adding this isn't the end of the world.