rockchip: include hdcp.bin and declare hdcp key decryption handler

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>