ASoC: mmp-sspa: Staticize non exported struct

The mmp_sspa_dai struct is only used in mmp-sspa.c, so make it static.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/pxa/mmp-sspa.c b/sound/soc/pxa/mmp-sspa.c
index a647799..62142ce 100644
--- a/sound/soc/pxa/mmp-sspa.c
+++ b/sound/soc/pxa/mmp-sspa.c
@@ -388,7 +388,7 @@
 	.set_fmt	= mmp_sspa_set_dai_fmt,
 };
 
-struct snd_soc_dai_driver mmp_sspa_dai = {
+static struct snd_soc_dai_driver mmp_sspa_dai = {
 	.probe = mmp_sspa_probe,
 	.playback = {
 		.channels_min = 1,