msm_fb: Restructure PCC and AR-GC code for clean implementation

Current PCC & AR-GC implementation uses macros for base
addresses, while other post processing features use
mdp_block2base() function. Also, in current implementation
check for feature supported for MDP version in device is not
performed, currently function which implements AR-GC, is
named as mdp4_pgc_cfg() which is bit misnomer.

This change uses uniform method for calculating block base
using mdp_block2base(). For checking MDP version and
feature supported using mdp_pp_block2pcc() and
mdp_pp_block2argc() functions.

This change also renames mdp4_pgc_cfg() to mdp4_argc_cfg() to
correctly indicate the functionality it implements.

Change-Id: I99a9948c987e3270c246aa44e569f94e35026c2f
Signed-off-by: Pravin Tamkhane <pravint@codeaurora.org>