Currently BCB command-line, C APIs and implementation only
support MMC interface. Extend it to allow various block
device interfaces.

Signed-off-by: Dmitrii Merkurev <dimorinny@google.com>
Cc: Eugeniu Rosca <erosca@de.adit-jv.com>
Cc: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
Cc: Simon Glass <sjg@chromium.org>
Cc: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Cc: Sean Anderson <sean.anderson@seco.com>
Cc: Cody Schuffelen <schuffelen@google.com>
Tested-by: Mattijs Korpershoek <mkorpershoek@baylibre.com> # on vim3
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>

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>