drm/hdcp: Expand HDCP helper library for enable/disable/check

Expand upon the HDCP helper library to manage HDCP enable, disable, and check.

Previous to this patch, the majority of the state management and sink
interaction is tucked inside the Intel driver with the understanding
that once a new platform supported HDCP we could make good decisions
about what should be centralized. With the addition of HDCP support
for Qualcomm, it's time to migrate the protocol-specific bits of HDCP
authentication, key exchange, and link checks to the HDCP helper.

In terms of functionality, this migration is 1:1 with the Intel driver,
however things are laid out a bit differently than with intel_hdcp.c,
which is why this is a separate patch from the i915 transition to the
helper. On i915, the shim vtable is used to account for HDMI vs. DP
vs. DP-MST differences whereas the helper library uses a LUT to
account for the register offsets and a remote read function to route
the messages. On i915, storing the sink information in the source is
done inline whereas now we use the new drm_hdcp_helper_funcs vtable
to store and fetch information to/from source hw. Finally, instead of
calling enable/disable directly from the driver, we'll leave that
decision to the helper and by calling drm_hdcp_helper_atomic_commit()
from the driver. All told, this will centralize the protocol and state
handling in the helper, ensuring we collect all of our bugs^Wlogic
in one place.

Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Mark Yacoub <markyacoub@chromium.org>