drm/i915: Increase timeout for Encrypt status change

At enable/disable of the HDCP encryption, for encryption status change
we need minimum one frame duration. And we might program this bit any
point(start/End) in the previous frame.

With 20mSec, observed the timeout for change in encryption status.
Since this is not time critical operation and we need to hold on
until the status is changed, fixing the timeout to 50mSec. (Based on
trial and error method!)

v2:
  %s/TIME_FOR_ENCRYPT_STATUS_CHANGE/ENCRYPT_STATUS_CHANGE_TIMEOUT_MS
	[Sean Paul]

Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Sean Paul <sean@poorly.run>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1544010283-20223-5-git-send-email-ramalingam.c@intel.com