fix(handoff): correct representation of tag_id

The tag ID is a 3-byte field used to identify the contents of a TE. In
our library, the internal representation of the tag is a 2 byte field.
We currently ignore the top byte of this field, marking it res0. This
causes problems when dealing with non-standard TE types, whose range
starts at 0xff_f000.  This commit fixes this by using a bit-field with a
24-bit width, and packing `transfer_list_entry`.

Change-Id: Ib3c212f964b64f528ad6f3dd6ab8b4597b877cd9
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
2 files changed