doc: boards: amlogic: update documentation for index page

doc: boards: amlogic: update documentation for index page

Improve documentation. Notably we remove all the board names from the
feature matrix to reduce table width. SoC types have been added to the
titles in individual board documents so readers can still correlate a
board against the features. This makes it easier to add new boards to
to the document in the future.

Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Link: https://lore.kernel.org/r/20230320114609.930145-2-christianshewitt@gmail.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>