LV_COLOR_SWAP_16 has incorrect dependencies across Zephyr

[danieldegrasse]

Describe the bug
The KConfig LV_COLOR_SWAP_16 is defined to depend on LV_COLOR_DEPTH_16 within LVGL itself: https://github.com/zephyrproject-rtos/lvgl/blob/a76caad0aa99838bb7a3315aaaf07e50d595c284/Kconfig#L40

However, many shields or boards in Zephyr simply enable this setting if LVGL is enabled, since they assume LVGL will be built with LV_COLOR_DEPTH_16 when targeting that shield/board. For example, see here:

zephyr/boards/weact/mini_stm32h743/Kconfig.defconfig

Line 16 in 4789820

default y

This assumption is broken if a sample or user manually selects the LVGL color depth setting, such as in the transparency sample:

zephyr/samples/modules/lvgl/screen_transparency/prj.conf

Line 6 in 4789820

CONFIG_LV_COLOR_DEPTH_32=y

This results in a build error, since LV_COLOR_DEPTH_16 should not logically be enabled.

Please also mention any information which could help others to understand
the problem you're facing:

• What target platform are you using? m5stack_atoms3/esp32s3/procpu

To Reproduce
Steps to reproduce the behavior:

1. west build -p -b m5stack_atoms3/esp32s3/procpu samples/modules/lvgl/screen_transparency -T sample.modules.lvgl.screen_transparency

Expected behavior

Setting the choice Kconfig LV_COLOR_DEPTH should be possible without inducing a build error.

Impact
Blocking CI on #81293

Logs and console output

n.c.obj -c /home/danieldegrasse/zephyr/zephyrproject/zephyr/samples/modules/lvgl/screen_transparency/src/main.c
In file included from /home/danieldegrasse/zephyr/zephyrproject/modules/lib/gui/lvgl/src/../src/hal/../draw/../misc/lv_style.h:19,
                 from /home/danieldegrasse/zephyr/zephyrproject/modules/lib/gui/lvgl/src/../src/hal/../draw/lv_draw.h:18,
                 from /home/danieldegrasse/zephyr/zephyrproject/modules/lib/gui/lvgl/src/../src/hal/lv_hal_disp.h:21,
                 from /home/danieldegrasse/zephyr/zephyrproject/modules/lib/gui/lvgl/src/../src/hal/lv_hal.h:16,
                 from /home/danieldegrasse/zephyr/zephyrproject/modules/lib/gui/lvgl/src/../lvgl.h:33,
                 from /home/danieldegrasse/zephyr/zephyrproject/modules/lib/gui/lvgl/src/lvgl.h:17,
                 from /home/danieldegrasse/zephyr/zephyrproject/zephyr/samples/modules/lvgl/screen_transparency/src/main.c:11:
/home/danieldegrasse/zephyr/zephyrproject/modules/lib/gui/lvgl/src/../src/hal/../draw/../misc/lv_color.h:27:2: error: #error "LV_COLOR_16_SWAP requires LV_COLOR_DEPTH == 16. Set it in lv_conf.h"
   27 | #error "LV_COLOR_16_SWAP requires LV_COLOR_DEPTH == 16. Set it in lv_conf.h"
      |  ^~~~~
[30/433] Building C object zephyr/CMakeFiles/zephyr.dir/lib/utils/rb.c.obj
ninja: build stopped: subcommand failed.
FATAL ERROR: command exited with status 1: /usr/bin/cmake --build /home/danieldegrasse/zephyr/zephyrproject/zephyr/build

Environment (please complete the following information):

• OS: Ubuntu 22.04 LTS
• Toolchain Zephyr SDK 0.17.0-rc1
• Commit SHA or Version used 4789820 (main)