audio-hal: Fix audio makefile violations

makefile violations fixed as reported by scanner tool to remove
local_copy_headers which is deprecated,Instead use
LOCAL_EXPORT_C_INCLUDE_DIRS.These allow access to the
headers automatically if linked to the associated code. Also replaced
TARGET_PRODUCT with TARGET_BOARD_PLATFORM as per scanner tool
suggestion.

Change-Id: I2a42adcaa5e643f2e04c138651bb43525964fd8c