d/patches: Revert RPi from bootstd to distroboot booting

The RPi support has shifted to bootstd and using a text env, however we
need the older distroboot for our rollback strategy. Revert the config
changes as far as possible that changed the boot methods. The
environment variables that would normally be added to the u-Boot env
when distroboot is enabled won't be as that process requires the env to
be in the include files (rather than stored as a text file). We don't
want to revert all the changes from moving to the text env, so add the
environment variables that were previously added in the defines to the
relevant text env file.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>