mcu-lvgl-trainer, mcu-lvgl-eworkbench: migrate display to mipi_spi

qspi_dbi is deprecated in favor of mipi_spi. Also fixes
mcu-lvgl-trainer's LVGL rotation (must be set on the lvgl component,
not the display, when LVGL is in use) and its deprecated
publish_initial_state -> trigger_on_initial_state. brightness is
dropped since mipi_spi only supports it for AMOLED panels and both
devices already control backlight separately.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

mcu-lvgl-eworkbench.yaml

@@ -105,8 +105,8 @@ power_supply:
   enable_on_boot: true
 
 display:
-  - platform: qspi_dbi
-    model: axs15231
+  - platform: mipi_spi
+    model: AXS15231
     data_rate: 40MHz #20mhz is default
     #spi_mode: MODE2
     id: main_display
@@ -115,7 +115,6 @@ display:
       height: 480
       width: 320
     cs_pin: 45
-    brightness: 50
     rotation: 90
     auto_clear_enabled: false
     show_test_card: true