Use audio_format_t consistently

Change-Id: I7eb489b1c1cbe9bfadd43cd7645da86b90fab652
diff --git a/include/system/audio.h b/include/system/audio.h
index 52ba5e7..0f19101 100644
--- a/include/system/audio.h
+++ b/include/system/audio.h
@@ -382,7 +382,7 @@
         return false;
 }
 
-static inline bool audio_is_valid_format(uint32_t format)
+static inline bool audio_is_valid_format(audio_format_t format)
 {
     switch (format & AUDIO_FORMAT_MAIN_MASK) {
     case AUDIO_FORMAT_PCM:
@@ -403,12 +403,12 @@
     }
 }
 
-static inline bool audio_is_linear_pcm(uint32_t format)
+static inline bool audio_is_linear_pcm(audio_format_t format)
 {
     return ((format & AUDIO_FORMAT_MAIN_MASK) == AUDIO_FORMAT_PCM);
 }
 
-static inline size_t audio_bytes_per_sample(uint32_t format)
+static inline size_t audio_bytes_per_sample(audio_format_t format)
 {
     size_t size = 0;