target: msm8996: decouple display resource manager

Current hardware interface enablement has coupled hardware
resource manager together, it's not good from software's
perspective. So decouple this hardware resource manager and
move it to one new file mdp5_rm.c.

Change-Id: I0e3e8965fb4e2b1716050a76095a6cbe76a32f6d
Signed-off-by: Guchun Chen <guchunc@codeaurora.org>