Documentation: ublk: Separate UBLK_F_AUTO_BUF_REG fallback behavior sublists

Stephen Rothwell reports htmldocs warning on ublk docs:

Documentation/block/ublk.rst:414: ERROR: Unexpected indentation. [docutils]

Fix the warning by separating sublists of auto buffer registration
fallback behavior from their appropriate parent list item.

Fixes: ff20c51 ("ublk: document auto buffer registration(UBLK_F_AUTO_BUF_REG)")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/linux-next/20250612132638.193de386@canb.auug.org.au/
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Link: https://lore.kernel.org/r/20250613023857.15971-1-bagasdotme@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: bagasme

Documentation/block/ublk.rst

@@ -408,13 +408,15 @@ Fallback Behavior
 If auto buffer registration fails:
 
 1. When ``UBLK_AUTO_BUF_REG_FALLBACK`` is enabled:
+
    - The uring_cmd is completed
    - ``UBLK_IO_F_NEED_REG_BUF`` is set in ``ublksrv_io_desc.op_flags``
    - The ublk server must manually deal with the failure, such as, register
      the buffer manually, or using user copy feature for retrieving the data
      for handling ublk IO
 
 2. If fallback is not enabled:
+
    - The ublk I/O request fails silently
    - The uring_cmd won't be completed