A default resolution in the ssd130x driver isn't set to an arbitrary 96x16
anymore. Instead is set to a width and height that's controller dependent.

The datasheets for the chips describes the following display resolutions:

 - SH1106:  132 x 64 Dot Matrix OLED/PLED
 - SSD1305: 132 x 64 Dot Matrix OLED/PLED
 - SSD1306: 128 x 64 Dot Matrix OLED/PLED
 - SSD1307: 128 x 39 Dot Matrix OLED/PLED
 - SSD1309: 128 x 64 Dot Matrix OLED/PLED

Update DT schema to reflect what the driver does and make its users aware.
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230609170941.1150941-3-javierm@redhat.com