UPSTREAM: drm/i915: Check for downstream topology errors

HDCP compliant Repeaters can support max of 127 devices and max
depth of 7 for downstream topology.

If these max limits are exceeded, repeater will set the
topology error flags MAX_CASCADE_EXCEEDED and/or MAX_DEVS_EXCEEDED
in Bstatus followed by asserting READY/CP_IRQ for HDCP transmitter.

This patch check for these error flags as soon as READY bit is asserted.

Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
[seanpaul fixed checkpatch alignment issue]
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1516254488-4971-5-git-send-email-ramalingam.c@intel.com
(cherry picked from commit 49d85d034268ab9d9156ff6f81cc07d4caad03f6)
Signed-off-by: Sean Paul <seanpaul@chromium.org>

Change-Id: I366ca1f946813854a06418e4923a922b2a8fe404
Reviewed-on: https://chromium-review.googlesource.com/877083
Commit-Ready: Sean Paul <seanpaul@google.com>
Tested-by: Sean Paul <seanpaul@google.com>
Reviewed-by: Kristian H. Kristensen <hoegsberg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/878779
Reviewed-by: Sean Paul <seanpaul@google.com>
Commit-Queue: Sean Paul <seanpaul@google.com>