boards: weact: mini_stm32h743: update ST7735R dts configuration

Update dts to use ST7735R via MIPI DBI API.

Also, remove the reset-gpios, as on this board the LCD RESET pin is
directly connected to the system reset. And add LCD backlight pin
connected to PE10.

Signed-off-by: Charles Dias <charlesdias.cd@outlook.com>