Convert Android documentation from regular txt format to Sphinx (RST).
Also add Android index.rst file and reference it in root index.rst, so
that Android documentation is visible.

Test:

    $ make htmldocs
    $ xdg-open doc/output/index.html

Signed-off-by: Sam Protsenko <joe.skb7@gmail.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>

We inconsistently note multiple dependencies today in our tests,
sometimes with a single line that declares multiple and sometimes
multiple single lines.  Current pytest seems to fail on the single line
format so change to multiple declarations.

Reviewed-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Simon Glass <sjg@chromium.org> [on sandbox]
Signed-off-by: Tom Rini <trini@konsulko.com>

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>