By default, U-boot sends the console output to both uart and video.
This commit suppresses the video output (where the boot logo is displayed)

The U-boot console output was temporarily suppressed to prevent it from overlapping with
the boot logo. This commit re-enables it.

Enable UART by default for raspberryPi.
With this variable set, meta-raspberrypi will add enable_uart=1 to config.txt and set
the correct tty in the kernel cmdline args

* The submodule points to the repository containing all CI/CD files
* Insert .gitlab-ci.yml file importing file for automatic manifest
integration

revert the effects of this commit in meta-raspberrypi: 80a12f7fddfeae28c43242765374e7ade3a2a59e
which sets some modules in the kernel config from y to m and causes psplash and the entire OS to hang shortly after boot

exclude the recipe in meta-raspberrypi that sets the raspberry icon as the psplash image

By default the kernel logo is displayed at the top-left corner of the screen and it's repeated $(nproc) times.
Set logo-pos and logo-count params for fbcon so that the logo image is cenetered and not repeated.

- display the splash screen
- enable the splaspos environment variable to configure positioning of the splash image
- enable the splashsource library, which allows to load the logo image from a custom source (see README.splashprepare)
- quiet console messages (see README.silent), which would otherwise overlap with the logo image
- enable CONFIG_SILENT_U_BOOT_ONLY to prevent U-boot from adding "quiet" to the bootargs, which would also hide the kernel logo
- NOTE: in the future we might want to direct the console output to the GPIO serial instead of silencing it entirely