19937: drivers/lcd: add MCU 8080 16-bit parallel mode support r=benpicco a=gschorcht
### Contribution description
This PR adds the 16-bit support for MCU 8080 parallel mode for LCD driver ICs.
### Testing procedure
Use either PR #19938
```
BOARD=stm32l496g-disco make -j8 -C tests/drivers/st77xx
```
or #19939 on top of this PR to test.
```
BOARD=sstm32f723e-disco make -j8 -C tests/drivers/st77xx
```
### Issues/PRs references
Prerequisite for PR #19938 or PR #19938
Co-authored-by: Gunar Schorcht <gunar@schorcht.net>
If a board definition already used the ST7735 driver, `st7735*.h` header files and `ST7735_*` macros were used in the board definitions to define the default configuration parameter set. For backward compatibility these header files are kept and the `ST7735_*` macros are mapped to the `ST77XX_*` macros if they are defined.
