Add APIs to defragment a sequence of 802.11 element/subelement
fragments. Add an inline mode to carry out the defragmentation within
the source buffer in order to reduce buffer requirements and to
eliminate memory copies/moves for the lead element/sublement.
Conversely, add a non-inline mode to copy the defragmented payload to
a separate buffer.
Add common helper functionality shared between these APIs.
CRs-Fixed: 3124132
Change-Id: Ia68584e918ddcf626b748f2b0c3a5da6492b40b6
3f38db23d4