apmanager: parse ap mode support information

Parse AP mode support information from Wiphy capability message. And do
not set preferred AP mode interface if AP mode is not supported.

BUG=chromium:431763
TEST=USE="asan clang" FEATURES=test emerge-$BOARD apmanager
Manual Test:
1. Verify AP service can be started on a device that supports AP mode.
2. Verify AP service failed to start on a device that doesn't
   support AP mode with a "No device available" error message.

Change-Id: Ia77fa3d74b944b978697afcb16aa71f27412fbdb
Reviewed-on: https://chromium-review.googlesource.com/233773
Reviewed-by: Peter Qiu <zqiu@chromium.org>
Commit-Queue: Peter Qiu <zqiu@chromium.org>
Trybot-Ready: Peter Qiu <zqiu@chromium.org>
Tested-by: Peter Qiu <zqiu@chromium.org>
3 files changed