boards: add a menu surrounding board Kconfig

This adds a menu to enclose all board Kconfig. So the board
configs do not appear on the top level out of context in
menuconfig. This also reflects the SoC options where these are
under menus for each architecture.

Change-Id: I76ce2bf1acf7cbd2673ceb2eac71e96cdca2ff35
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
1 file changed