fix spelling detected by lintian

Change-Id: I01e54b5cf111677079a8ad57645d3ceb7834702a
diff --git a/include/osmocom/msc/gsm_data.h b/include/osmocom/msc/gsm_data.h
index f6e3ed9..6050113 100644
--- a/include/osmocom/msc/gsm_data.h
+++ b/include/osmocom/msc/gsm_data.h
@@ -79,7 +79,7 @@
 	[MSC_CTR_SMS_DELIVERED] = 		{"sms:delivered", "Global SMS Deliver attempts."},
 	[MSC_CTR_SMS_RP_ERR_MEM] = 		{"sms:rp_err_mem", "CAUSE_MT_MEM_EXCEEDED errors of MS responses on a sms deliver attempt."},
 	[MSC_CTR_SMS_RP_ERR_OTHER] = 		{"sms:rp_err_other", "Other error of MS responses on a sms delive attempt."},
-	[MSC_CTR_SMS_DELIVER_UNKNOWN_ERROR] =	{"sms:deliver_unknown_error", "Unknown error occured during sms delivery."},
+	[MSC_CTR_SMS_DELIVER_UNKNOWN_ERROR] =	{"sms:deliver_unknown_error", "Unknown error occurred during sms delivery."},
 	/* FIXME: count also sms delivered */
 	[MSC_CTR_CALL_MO_SETUP] = 		{"call:mo_setup", "Received setup requests from a MS to init a MO call."},
 	[MSC_CTR_CALL_MO_CONNECT_ACK] = 		{"call:mo_connect_ack", "Received a connect ack from MS of a MO call. Call is now succesful connected up."},