drm/msm/sde: use current encoders to determine crtc interface

Instead of using the cached interface type, which is updated
during fence preparation time, determine interface type by
enumerating over all matching encoders and query the interface
directly. This avoids pontential stale interface types due to
changing connector state.

CRs-Fixed: 2009714
Change-Id: I31e1350cc62cafb5f014c0f32514d0692dec42d0
Signed-off-by: Alan Kwong <akwong@codeaurora.org>