accel/amdxdna: fix open_ref leak and stale client pointer on dma map failure

accel/amdxdna: fix open_ref leak and stale client pointer on dma map failure

amdxdna_gem_obj_open() increments open_ref before attempting to set up
the DMA address mapping.  When amdxdna_dma_map_bo() fails, the function
returned immediately without rolling back either change made on the first
open (open_ref == 1 path).

Fix it by decrementing open_ref and clearing abo->client on the error path.

Fixes: ece3e8980907 ("accel/amdxdna: Allow forcing IOVA-based DMA via module parameter")
Reviewed-by: Max Zhen <max.zhen@amd.com>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20260707055658.479049-1-lizhi.hou@amd.com