fs: fix __sb_write_started() kerneldoc formatting

fs: fix __sb_write_started() kerneldoc formatting

When running 'make htmldocs', I see the following warning:

  Documentation/filesystems/api-summary:14: ./include/linux/fs.h:1659: WARNING: Definition list ends without a blank line; unexpected unindent.

The official guidance [1] seems to be to use lists, which will prevent
both the "unexpected unindent" warning as well as ensure that each line
is formatted on a separate line in the HTML output instead of being
all considered a single paragraph.

[1]: https://docs.kernel.org/doc-guide/kernel-doc.html#return-values

Fixes: 8802e580ee64 ("fs: create __sb_write_started() helper")
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Link: https://lore.kernel.org/r/20231228100608.3123987-1-vegard.nossum@oracle.com
Signed-off-by: Christian Brauner <brauner@kernel.org>