dma-buf: fix dma_buf_export init order v2

The init order and resulting error handling in dma_buf_export
was pretty messy.

Subordinate objects like the file and the sysfs kernel objects
were initializing and wiring itself up with the object in the
wrong order resulting not only in complicating and partially
incorrect error handling, but also in publishing only halve
initialized DMA-buf objects.

Clean this up thoughtfully by allocating the file independent
of the DMA-buf object. Then allocate and initialize the DMA-buf
object itself, before publishing it through sysfs. If everything
works as expected the file is then connected with the DMA-buf
object and publish it through debugfs.

Also adds the missing dma_resv_fini() into the error handling.

v2: add some missing changes to dma_bug_getfile() and a missing NULL
    check in dma_buf_file_release()

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Reviewed-by: T.J. Mercier <tjmercier@google.com>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221209071535.933698-1-christian.koenig@amd.com