dts/st: add LTDC signals

Add LTDC signals on all targets that support an LTDC peripheral (F4, L4, F7, H7 and MP1)

(cherry picked from commit 34fe6f7332925417b5c7fbd1eed2414b2741c2e4)

GitOrigin-RevId: 34fe6f7332925417b5c7fbd1eed2414b2741c2e4
Change-Id: Ibc1df73c80574612d19c0b11a9d96d3a59a6e16b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/hal_stm32/+/3348701
Tested-by: CopyBot Service Account <copybot.service@gmail.com>
Reviewed-by: Tristan Honscheid <honscheid@google.com>
Reviewed-by: Aaron Massey <aaronmassey@google.com>
Commit-Queue: Aaron Massey <aaronmassey@google.com>