Check netboot using kernel cmdline argument 'cros_netboot'

We can check bootarg by checking kernel cmdline for cros_netboot flag.

BUG=chrome-os-partner:16705
TEST=build install shim and run netboot firmware on link with kernel
cmdline argument 'cros_netboot'. Can install factory package properly.

Change-Id: I414baa082303c8af024f2ccfc72b90cb6f0710a6
Reviewed-on: https://gerrit.chromium.org/gerrit/39460
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Commit-Ready: Cheng-Yi Chiang <cychiang@chromium.org>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>
1 file changed