fs: inode.c: get rid of docs warnings

Use *foo makes the toolchain to think that this is an emphasis, causing
those warnings:

	./fs/inode.c:1609: WARNING: Inline emphasis start-string without end-string.
	./fs/inode.c:1609: WARNING: Inline emphasis start-string without end-string.
	./fs/inode.c:1615: WARNING: Inline emphasis start-string without end-string.

So, use, instead, ``*foo``, in order to mark it as a literal block.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/e8da46a0e57f2af6d63a0c53665495075698e28a.1586881715.git.mchehab+huawei@kernel.org


Signed-off-by: Jonathan Corbet <corbet@lwn.net>