bloblist: Adjust the bloblist header

The v0.9 spec provides for a 24-byte header. Update the implementation
to match this.
Rename the fields of the bloblist header to align to the spec.
Adds an alignment field into the bloblist header.
Update the related bloblist APIs and UT testcases.

Signed-off-by: Simon Glass <sjg@chromium.org>
Co-developed-by: Raymond Mao <raymond.mao@linaro.org>
Signed-off-by: Raymond Mao <raymond.mao@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>