env: Initialise all the environments

Since we want to have multiple environments, we will need to initialise
all the environments since we don't know at init time what drivers might
fail when calling load.

Let's init all of them, and only consider for further operations the ones
that have not reported any errors at init time.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>