libbpf: fix extraversion in makefile to that of upstream

Backport in f49907472f00 ("sync: latest libbpf changes from kernel")
missed to bump Makefile's EXTRAVERSION to 3.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
diff --git a/src/Makefile b/src/Makefile
index 35b4818..e9021fe 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -2,7 +2,7 @@
 
 VERSION = 0
 PATCHLEVEL = 0
-EXTRAVERSION = 2
+EXTRAVERSION = 3
 
 LIBBPF_VERSION	= $(VERSION).$(PATCHLEVEL).$(EXTRAVERSION)