Revert "scsi: core: Use a structure member to track the SCSI command submitter"

This reverts commit 8f2350e2 which is
commit bf23e619 upstream.

It breaks the Android KABI and is not needed at this time for any
Android-relevant systems.

Bug: 161946584
Change-Id: I156b994dbccedface36e892e24fc439406b6c34b
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>