drivers: dma-buf: replace dma_buf_put with fput in free_proc

free_proc does a dma_buf_put to free the reference taken by
get_dma_info. But get_dma_info takes the reference using get_file.
This causes the dma-buf-ref code to save stack references only on
put and thus dma_buf_ref_show shows incorrect total references.

Change-Id: Ib7c7599c13a9e0875bda06925da4191fe3ed8cc7
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>