drm/msm/mdp5: Create only as many CRTCs as we need

drm/msm/mdp5: Create only as many CRTCs as we need

We currently create CRTCs equaling to the # of Layer Mixer blocks we
have on the MDP5 HW. This number is generally more than the # of encoders
(INTFs) we have in the MDSS HW. The number of encoders connected to
displays on the platform (as described by DT) would be even lesser.

Create only N drm_crtcs, where N is the number of drm_encoders
successfully registered. To do this, we call modeset_init_intf() before
we init the drm_crtcs and drm_planes.

Because of this change, setting encoder->possible_crtcs needs to be moved
from construct_encoder() to a later point when we know how many CRTCs we
have.

Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>