Add a new method to retrieve active usb keyboard modifiers.
Change-Id: Ief6679ce782b58b9ced207f4f27504fb2a517b76
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/18602
Reviewed-by: Martin Roth <martinroth@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>