Revert "hikey960: Remove hifi dsp support."

This reverts commit 1d7e5889cd761a9eaecb130c52582d2b0707a08d.

Reason for revert: previous commit broke build_test target, b/219798815

Change-Id: If678459053b79b81de27a1b7d514cc0c6101d97d
diff --git a/audio/audio_hw.c b/audio/audio_hw.c
index 3fdf3f9..02ce250 100644
--- a/audio/audio_hw.c
+++ b/audio/audio_hw.c
@@ -42,6 +42,7 @@
 #include <audio_effects/effect_aec.h>
 
 #include <sys/ioctl.h>
+#include <linux/audio_hifi.h>
 
 #define CARD_OUT 0
 #define PORT_CODEC 0