boot: Rename Android-boot text

Phrases like 'Enable support for' are pointless since this is an option
which enables things. Drop that part so it is easier to follow.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Reviewed-by: Tom Rini <trini@konsulko.com>