texi2html: fix packages warning

texi2html: fix packages warning

Add documentation to the -docs package

WARNING: For recipe texi2html, the following files/directories were installed but not shipped in any package:
WARNING:   /usr/share/texinfo
WARNING:   /usr/share/texinfo/html
WARNING:   /usr/share/texinfo/init
WARNING:   /usr/share/texinfo/html/texi2html.html
WARNING:   /usr/share/texinfo/init/html32.init
WARNING:   /usr/share/texinfo/init/tex4ht.init
WARNING:   /usr/share/texinfo/init/mediawiki.init
WARNING:   /usr/share/texinfo/init/book.init
WARNING:   /usr/share/texinfo/init/chm.init
(From OE-Core rev: 6db5deeea2aff2146d7957246702a76cd4cd7a14)

Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>