Tidy up conditional targets.

[prenticedavid]

dear lcdwiki,

I was asked to check out your library by a SSD1283A owner.
I do not have an SSD1283 but I did test with ILI9341 and ST7735S on Uno, Due, Teensy3.2, ESP32, Nucleo-64 targets.

Conditional register types mean that the same fast Port access statements can be used for "digitalWrite".
I had to move SPI peripheral access from constructor() to begin()
ARM targets can not access peripherals in the constructor because the clocks have not been configured.

Note that the ILI9325 has a different SPI format to ILI9325D.
And ILI9486 uses a different SPIREAD_CMD register and EN bit to the ILI9341.

The SSD1283 owner has gone silent. So the code is untested with SSD1283.
I would have preferred not to open a Pull Request before it was tested.

There is a trivial Pull Request for the LCDWIKI_gui

David.