Revert "scsi: core: Introduce enum scsi_disposition"

This reverts commit 7efadce4 which is
commit b8e162f9 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I4d61091819d54c290cfe08152daab17cfb7a3fa5
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>