docs: filesystems: vfs: Fix pre-amble indentation

Currently file pre-amble contains custom indentation.  RST is not going
to like this, lets left-align the text.  Put the copyright notices in a
list in preparation for converting document to RST.

Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>