audio: Support 64bit configuration on 32+64bit compatible OS

The default value is 'prefer32', in order to run the hardware audio
service as 64 bit on a 32+64bit OS, please add the content below
into 'device.mk':

SOONG_CONFIG_NAMESPACES += android_hardware_audio
SOONG_CONFIG_android_hardware_audio += \
	run_64bit
SOONG_CONFIG_android_hardware_audio_run_64bit := true

Bug: 205240941
Test: build pass
Signed-off-by: Carter Hsu <carterhsu@google.com>
Change-Id: Ic7632a4f80298721512cd538ce93945b82a9981f