drivers: mipi_dbi: add support for parallel 8080/6800 modes using GPIO

Introduce GPIO-based driver for MIPI DBI class that allows MIPI DBI
type A and B displays to be used on general platforms.

Since each data pin GPIO can be selected individually, the bus pins are
set in a loop, which has a significant negative impact on performance.
When using 8-bit mode and all the data GPIO pins are on the same port,
a look-up table is generated to set the whole port at once as a
performance optimization. This creates a ROM overhead of about 1 kiB.

Tested 8-bit 8080 mode with ILI9486 display on nRF52840-DK board.

Signed-off-by: Stefan Gloor <code@stefan-gloor.ch>