accel/amdxdna: Fix potential NULL pointer dereference of abo->client

accel/amdxdna: Fix potential NULL pointer dereference of abo->client

Closing a BO handle clears abo->client, while the underlying GEM object
may remain alive due to internal kernel references. As a result, code
executed after the BO handle is closed may dereference a NULL abo->client
pointer.

Remove accesses to abo->client from code paths that may execute after the
BO handle has been closed.

Fixes: d76856beb4a4 ("accel/amdxdna: Refactor GEM BO handling and add helper APIs for address retrieval")
Reviewed-by: Max Zhen <max.zhen@amd.com>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20260707201556.562191-1-lizhi.hou@amd.com