Some hashing commands permit saving the hash in an environment variable,
and verifying a hash from there. But the crc32 command does not support
this. In order to permit crc32 to use the generic hashing infrastructure,
add a flag to select which behaviour to use.
Signed-off-by: Simon Glass <sjg@chromium.org>
We have a SHA1 command and want to add a SHA256 command also. Instead of
duplicating the code, create a generic hash API which can process
commands for different algorithms.
Signed-off-by: Simon Glass <sjg@chromium.org>