fs: Fix kernel-doc warnings

[ Upstream commit 35931eb3 ]

These have a variety of causes and a corresponding variety of solutions.

Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Message-Id: <20230818200824.2720007-1-willy@infradead.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Stable-dep-of: c34706ac ("ovl: fix regression in parsing of mount options with escaped comma")
Signed-off-by: Sasha Levin <sashal@kernel.org>