Add a function to check if a packet is ours

This allows the ping socket codepaths to be simpler.

Bug: 9469682
Change-Id: I05174cafd74ad5de5e867af8a3a3ac19439034b4
diff --git a/ping_common.c b/ping_common.c
index 0342e1a..124270a 100644
--- a/ping_common.c
+++ b/ping_common.c
@@ -1073,3 +1073,7 @@
 	fprintf(stderr, "\n");
 }
 
+inline int is_ours(uint16_t id) {
+	return id == ident;
+}
+