msm_fb: Display: proper configuration of pipes with Mixers

As the borderfill pipe is not supported in MDP4.0, add change
to correct the pipe configuration with Mixer for both Primary
and External interfaces.

Add borderfill checks to avoid misconfiguration of pipes to
avoid unnecessary pipe commits which results in underruns on
both primary and external.

CRs-fixed: 458732
CRs-fixed: 458283

Change-Id: I49173a6398bca5f7d7c356674d9e3db0997d37fe
Signed-off-by: Jeevan Shriram <jshriram@codeaurora.org>