fs: document 'name' parameter for name_contains_dotdot()

The kernel-doc for name_contains_dotdot() was missing the @name
parameter description, leading to a warning during make htmldocs.

Add the missing documentation to resolve this warning.

Signed-off-by: Kriish Sharma <kriish.sharma2006@gmail.com>
Link: https://lore.kernel.org/20250730201853.8436-1-kriish.sharma2006@gmail.com


Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>