drm/msm/sde: allow sde components creation from external module

Add capability of adding new sde components from external modules.

msm_drv: add maximum crtc/encoder/connector/bridge num to 16
sde_crtc: add priv_handle for external use
sde_encoder: add sde_encoder_ops callback function as init parameters
sde_rm: add ext h/w block creation, allow empty ctl/lm reservation

Change-Id: I66dcd824ccf4048c51068bd78538dd9e1aeac66b
Signed-off-by: Xiaowen Wu <wxiaowen@codeaurora.org>