boards: shields: x_nucleo_gfx01m2: add x_nucleo_gfx01m2 board support

The x_nucleo_gfx01m2 is an evaluation shield sold by
STMicroelectronics. It features a MIPI DBI SPI serial TFT LCD display
and a SPI NOR Flash for graphical assets storage. A button joystick
can be used to control the GUI.

Signed-off-by: Christian Rask <christianrask2@gmail.com>