Bug Fix release

This release removes (and desupports) a dependency on 32-bit color depth when
using LVGL, the color conversion code has only ever supported 16-bit color data
but was incorrectly casting the source color data to uint32_t instead of
uint16_t.

As a result of the above bug fix the esp_lcd_panel_dev_config_t field
bits_per_pixel will be ignored by esp_lcd_new_panel_ili9488 and the ILI9488
will always use the 18-bit color mode.

The LVGL example has been updated as below:

• Remove unused lvgl_port_update_callback since the example does not include
  touch support or any screen rotation API calls.
• Add option for enabling / disabling double buffering with LVGL, default is to
  use a single buffer.
• Added missing Kconfig.projbuild entry for TFT_RESET_PIN, added new entry
  DISPLAY_COLOR_MODE which can be used to toggle between BGR and RGB color mode
  on the ILI9488 display.
• Enhanced example to switch from only using lv_spinner_create to instead use
  lv_meter_create and lv_anim_t to display an animated gauge.
• Reduced default backlight brightness to 75%.
• Switched from using esp_register_freertos_tick_hook to esp_timer_create
  for the tick update handler.
• Add code to set the background color of the display to black.