trusty: Fix trusty_ffa_fill_desc return path

The "Add check that ffa buffer has been registered" patch added an early
return path to trusty_ffa_fill_desc, but did not destroy the incomplete
object like the other error paths do. Fix this.

Also destroy the object on invalid requests that would try fill past the
object size, and prevent any invalid request from destroying an already
completed objecti (for SMC_FC_FFA_MEM_FRAG_TX).

Bug: 185886292
Change-Id: I506a4f43ea6c8466478b94537140964a463310de
1 file changed