ASoC: Don't use -1 to boostrap subseq so it can be used by drivers

Makes life a little easier if you want to add subsequences to an existing
driver as you can use -1 to put things at the start of sequences.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
index 54fa2e5..fbfcda0 100644
--- a/sound/soc/soc-dapm.c
+++ b/sound/soc/soc-dapm.c
@@ -989,7 +989,7 @@
 
 			INIT_LIST_HEAD(&pending);
 			cur_sort = -1;
-			cur_subseq = -1;
+			cur_subseq = INT_MIN;
 			cur_reg = SND_SOC_NOPM;
 			cur_dapm = NULL;
 		}