LVGL_PIXEL_BUFFER_LINES as a define

[rzeldent]

LVGL_PIXEL_BUFFER_LINES is now hard coded to 16.

Unfortunately I found that config for board 8048S043C is too slow and CPU utilization is too high with this lib.

I hope that it is only config that is not properly optimized and that it will be fixed at some point so that I can start using it at some point.

maybe lvgl buffer config is too small - my buffer is 1/4 of total number of pixels - I don't know what is this lib default buffer size
maybe it is because I am using a different driver that is faster. I am using moononournation/GFX Library for Arduino@1.3.7 - I don't know what this library uses.
Also touch is not working. I did not have time to investigate why. I can see this library uses the correct chip GT911 for this board.

[rzeldent]

Is done with define. See issue #124