ALSA: pcm: add local header file for snd-pcm module

Several files are used to construct PCM core module, a.k.a snd-pcm.
Although available APIs are described in 'include/sound/pcm.h', some of
them are not exported as symbols in kernel space. Such APIs are just for
module local usage.

This commit adds module local header file and move some function prototypes
into it so that scopes of them are controlled properly and developers
get no confusion from unavailable symbols.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index d30dba0..4b32904 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -31,6 +31,8 @@
 #include <sound/control.h>
 #include <sound/info.h>
 
+#include "pcm_local.h"
+
 MODULE_AUTHOR("Jaroslav Kysela <perex@perex.cz>, Abramo Bagnara <abramo@alsa-project.org>");
 MODULE_DESCRIPTION("Midlevel PCM code for ALSA.");
 MODULE_LICENSE("GPL");