msm: mdss: hdmi: remove check for hdcp ops when starting hdcp

Checking if HDCP is enabled will ensure that HDCP 2.2
is enabled, in which case hdcp ops will be available.
Removing redundant check for hdcp ops. This prevents an
error log when EINVAL is unnecessarily returned to
mdp_intf.

Change-Id: I3f63dbd70651b15b241df9f3ebd4c1aab231fced
Signed-off-by: Casey Piper <cpiper@codeaurora.org>