video: mdss: LiveDisplay driver improvements

Author: Michael Bestas <mikeioannina@cyanogenmod.org>
video: mdss: Fix dual-DSI issue in LiveDisplay

* The second controller won't have it's own framebuffer, so don't
  dereference a NULL pointer.

Change-Id: I0cacbd0768a6a0f8e2ed934a8263aa75265f42b1

mdss: livedisplay: Add HBM support

* Adapted from oneplus3 implementation

Change-Id: I5a686ff72de04f59df6e4ee5cef4585252d8adfd

mdss: livedisplay: Add commands to enable SRGB mode

 * And add it to the DT. Originally from OP3 upstream and adapted
   to our nicer LiveDisplay interface.

Change-Id: I719372f2ea4eaf083aa874c1bd6c0453c03bc1a1

video: livedisplay: Allow setting DSI link state via DT

 * We need to send commands in LP mode for some hardware.

Change-Id: I96dacea6bcc52960f9f759981984752180a33464