topology: initialize variable for error output

topology: initialize variable for error output

This commit fixes below compiler warnings.

In file included from ../../include/local.h:165:0,
                 from tplg_local.h:17,
                 from data.c:20:
data.c: In function ‘tplg_parse_tuples’:
../../include/error.h:64:21: warning: ‘id’ may be used uninitialized in this function [-Wmaybe-uninitialized]
 #define SNDERR(...) snd_lib_error(__FILE__, __LINE__, __FUNCTION__, 0, __VA_ARGS__) /**< Shows a sound error message. */
                     ^
data.c:576:14: note: ‘id’ was declared here
  const char *id;
              ^

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>