sbc: Fix visibility of sbc_reinit_a2dp()

sbc_reinit_a2dp() is missing the SBC_EXPORT attribute so it's not
visibile to be used by consumers of the shared object.
diff --git a/sbc/sbc.c b/sbc/sbc.c
index 7f1efaa..edbe332 100644
--- a/sbc/sbc.c
+++ b/sbc/sbc.c
@@ -1191,7 +1191,7 @@
 	return 0;
 }
 
-int sbc_reinit_a2dp(sbc_t *sbc, unsigned long flags,
+SBC_EXPORT int sbc_reinit_a2dp(sbc_t *sbc, unsigned long flags,
 					const void *conf, size_t conf_len)
 {
 	int err;