For some reason, HDCP key decrytion can't open source in ATF, so we
build it as hdcp.bin. Besides declare the handler for decrypting.

Change-Id: Ia67ff2442ab43cb3ee4875b3d59cc1608e854b4b
Signed-off-by: Ziyuan Xu <xzy.xu@rock-chips.com>
Signed-off-by: Caesar Wang <wxt@rock-chips.com>