drivers/misc: skip revocation check if no device connected

There is no need to perform revocation check if no device
is connected. This will skip call to HDCP SRM TA and will
directly return success.

Change-Id: Ia55d8a7050410b71e818361b06a64f1a6b4697b8
Signed-off-by: Neeraj Soni <neersoni@codeaurora.org>