pcm_converter: do nothing when there are no samples

HiFi3 version of PCM converter can corrupt data or go into
endless loop, when called with samples = 0. Make sure
the processing functions return immediately if that happens.

Signed-off-by: Tomasz Lauda <tomasz.lauda@linux.intel.com>

src/audio/pcm_converter/pcm_converter_hifi3.c

@@ -52,6 +52,10 @@ static void pcm_convert_s16_to_s24(const struct audio_stream *source,
 	ae_int32x2 *out32x2;
 	int i = 0;
 
+	/* nothing to do */
+	if (!samples)
+		return;
+
 	/* required alignment for AE_L16X4_XC */
 	while (!IS_ALIGNED((uintptr_t)in, 8)) {
 		/* set source as circular buffer */
@@ -153,6 +157,10 @@ static void pcm_convert_s24_to_s16(const struct audio_stream *source,
 	int i = 0;
 	int leftover;
 
+	/* nothing to do */
+	if (!samples)
+		return;
+
 	/* required alignment for AE_L32X2_XC */
 	if (!IS_ALIGNED((uintptr_t)in, 8)) {
 		/* set source as circular buffer */
@@ -257,6 +265,10 @@ static void pcm_convert_s16_to_s32(const struct audio_stream *source,
 	ae_int32x2 *out32x2;
 	int i = 0;
 
+	/* nothing to do */
+	if (!samples)
+		return;
+
 	/* required alignment for AE_L16X4_XC */
 	while (!IS_ALIGNED((uintptr_t)in, 8)) {
 		/* set source as circular buffer */
@@ -338,6 +350,10 @@ static void pcm_convert_s32_to_s16(const struct audio_stream *source,
 	int i = 0;
 	int leftover;
 
+	/* nothing to do */
+	if (!samples)
+		return;
+
 	/* required alignment for AE_L32X2_XC */
 	if (!IS_ALIGNED((uintptr_t)in, 8)) {
 		/* set source as circular buffer */
@@ -436,6 +452,10 @@ static void pcm_convert_s24_to_s32(const struct audio_stream *source,
 	ae_valign align_out = AE_ZALIGN64();
 	int i;
 
+	/* nothing to do */
+	if (!samples)
+		return;
+
 	/* required alignment for AE_L32X2_XC */
 	if (!IS_ALIGNED((uintptr_t)in, 8)) {
 		/* set source as circular buffer */
@@ -522,6 +542,10 @@ static void pcm_convert_s32_to_s24(const struct audio_stream *source,
 	ae_valign align_out = AE_ZALIGN64();
 	int i;
 
+	/* nothing to do */
+	if (!samples)
+		return;
+
 	/* required alignment for AE_L32X2_XC */
 	if (!IS_ALIGNED((uintptr_t)in, 8)) {
 		/* set source as circular buffer */