Stop depending on libnl.

We only use it for trivial functions. Replace them and drop the
dependency.

Bug: 67345547
Test: bullhead builds, boots
Test: CtsOsTestCases android.os.cts.StrictModeTest passes
Change-Id: I36254962284babdd1a55a32a76dd0dc92d85420c
diff --git a/libsysutils/include/sysutils/NetlinkEvent.h b/libsysutils/include/sysutils/NetlinkEvent.h
index b80f3ea..f9fc11b 100644
--- a/libsysutils/include/sysutils/NetlinkEvent.h
+++ b/libsysutils/include/sysutils/NetlinkEvent.h
@@ -64,6 +64,7 @@
     bool parseNfPacketMessage(struct nlmsghdr *nh);
     bool parseRtMessage(const struct nlmsghdr *nh);
     bool parseNdUserOptMessage(const struct nlmsghdr *nh);
+    struct nlattr* findNlAttr(const nlmsghdr* nl, size_t hdrlen, uint16_t attr);
 };
 
 #endif