dma-buf: Remove dmabuf from db_list before releasing

commit "d8f41e97 ion: add additional debug info in dmabuf exp_info"
makes exp_name allocation dynamic and this could get freed while buffer
is still in release path, since ops->release is called before removing
the dmabuf from db_list.Calling dma_buf_debug_show at this point would
try accessing already freed exp_name as db_list still contains the dmabuf.
Fix it by removing the dmabuf from db_list and then invoke ops->release.

Change-Id: Ia3266cfee5b9cd7fe9716198730450b9c8d00b3c
Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>