Fix unsigned num comparison with zero

Caught by -Wtautological-unsigned-zero-compare compiler flag

Test: m
Change-Id: Ibedc657a237ba29fd7a4452271f347cd3180f57c
diff --git a/bpf/loader/NetBpfLoad.cpp b/bpf/loader/NetBpfLoad.cpp
index d70a2c8..4c47f83 100644
--- a/bpf/loader/NetBpfLoad.cpp
+++ b/bpf/loader/NetBpfLoad.cpp
@@ -769,7 +769,7 @@
     const size_t max_name = 256;
     char kvTypeName[max_name];
     int64_t keySize, valueSize;
-    uint32_t kvId;
+    int32_t kvId;
 
     if (snprintf(kvTypeName, max_name, "____btf_map_%s", mapName) == max_name) {
         ALOGE("____btf_map_%s is too long", mapName);