displayio: Option needed to allow SPI Chip Select Toggle between init commands

Due to the way the ST7789 display works, the only way I was able to get it to work was to have the CS briefly go High, then Low between commands. I found this by examining the Arduino Driver and it seems particular to this display. I have confirmed that toggling this in CircuitPython does fix the display working. I am preparing my first PR to fix this and will submit when it passes on Travis.