drm/msm: suppress display platform drivers bind/unbind feature

Display platform drivers does not support the manual bind/unbind
feature through sysfs. Suppress the bind/unbind calls using driver
attribute.

Change-Id: If583694c6bfe659e17e76a736f2fcfb52e6d1a01
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>