ns2: Add a rate_ctr for each NS-UNBLOCK

We have one for BLOCK, so let's also add one for UNBLOCK.

Change-Id: I693109b7bc4d72b6803b40aae15327389aa37c69
diff --git a/src/gb/gprs_ns2_internal.h b/src/gb/gprs_ns2_internal.h
index 98b3f29..e149767 100644
--- a/src/gb/gprs_ns2_internal.h
+++ b/src/gb/gprs_ns2_internal.h
@@ -93,6 +93,7 @@
 	NS_CTR_BYTES_OUT,
 	NS_CTR_BYTES_OUT_DROP,
 	NS_CTR_BLOCKED,
+	NS_CTR_UNBLOCKED,
 	NS_CTR_DEAD,
 	NS_CTR_REPLACED,
 	NS_CTR_NSEI_CHG,