Use better defines for TFT_LVGL_UI: SPI and FSMC version

[rhapsodyv]

Description

LVGL UI have two versions: SPI (used in Nano v2.0) and FSMC (used in Nano v1.2 and Chitu).

Before this PR, to use the FSMC version, you define TFT_LVGL_UI, but to use the SPI version, you had to define both: TFT_LVGL_UI and SPI_GRAPHICAL_TFT.

It can lead to confusion, because Marlin has other similar define: FSMC_GRAPHICAL_TFT, the emulated DOGM using FSMC. And SPI_GRAPHICAL_TFT looks like its the DOGM, but using SPI...

So, I changed the LVGL UI defines to better match with what Marlin follows. Now we have:

• TFT_LVGL_UI_FSMC -> LVGL for FSMC displays
• TFT_LVGL_UI_SPI -> LVGL for SPI displays

I removed references for SPI_GRAPHICAL_TFT, as in the future we may have a emulated DOGM using SPI, and can use that define when appropriated.

Benefits

• Follow the Marlin Standards
• Less confusion