Brush up audio parameters usage

It is preferred to use the constants from AudioParameter
(which can now serve as an abstraction layer similar to libaudiohal).

Grepped for usages of defines and just string values
and replaced with references to AudioParameter.

Since the parameter definitions are being moved to system/audio.h,
update includes in AudioParemeter and stagefright Utils.

Change-Id: I2addb983707d866b16f39d45d0e14b802595e292
Test: make