msm: mdss: Allow CMD panels for Assertive Display

Remove the check that prevented command mode panels from enabling assertive
display functionality.

Change-Id: Iecf0f518a45da556d1d9d0558a7d2dc572cc82da
Signed-off-by: Carl Vanderlip <carlv@codeaurora.org>
Signed-off-by: Ping Li <quicpingli@codeaurora.org>