Despite of comments in both files no-one ever adjusted start/end-line
in 'what-is-ovs' document. As a result, current document contains
truncated "tools" section.
Let's replace start/end-line with start-after/end-before which requires
less attention. Additionally, 'make docs-check' will fail if specified
lines will not be found, i.e it'll be harder to mess up the docs again.
"Fixes" tag points to commit that broke the lines first.
Fixes: 602e24ee189b ("doc: Remove experimental warning for DPDK.") Signed-off-by: Ilya Maximets <i.maximets@samsung.com> Acked-by: Stephen Finucane <stephen@that.guru>