Some files compiled into the default environment may be needed earlier in
the boot process, so move loading of the default environment to fs_initcall.
Only the default environment is loaded earlier, but not the overwriting with
the persistent environment files, so when the files are used that early, only
the compiled in version is available; it's not overwritable at that
time.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>