This patch implemented USB keyboard library and added it as an
input console device. It can be enabled by setting BIT1 in
self.CONSOLE_IN_DEVICE_MASK in BoardConfig.py. By default, it
will be disabled for performance and size consideration.
Test has been done on APL Leafhill board. USB keyboard can work
in Shell.
Signed-off-by: Maurice Ma <maurice.ma@intel.com>