Docs: Specify tools version

To have the better generated documentation format, sphinx should be
2.0.1 and docutils should be 0.16.
Package librsvg2-bin is needed by sphinxcontrib-svg2pdfconverter.

Signed-off-by: Summer Qin <summer.qin@arm.com>
Change-Id: Id001bf742378d6675ae3f5a73a6035824c8e4b2d
2 files changed