env: Move get/set_default_env() to env.h

Move these functions to the new header file and rename set_default_env()
to env_set_default() so that it has a consistent env_ prefix.

Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
15 files changed