drm/msm: scrambling not mandatory for DP interface

Scrambling high frequency resolutions which are greater than
340MHz is not mandatory for Display Port interface. Moreover
EDIDs of DP monitors supporting 4K60 may not even have HF-VSD
block to indicate SCDC and Scramble support. So, remove the
check to validate each mode against minimum required scrambler
rate (340MHz).

Change-Id: Ia24c0e18dac94a89feeeea66fea87a3df7633771
Signed-off-by: Narender Ankam <nankam@codeaurora.org>