libbpf: Fix KERNEL_VERSION macro

Add missing ')' for KERNEL_VERSION macro.
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210405040119.802188-1-hengqi.chen@gmail.com

tools/lib/bpf/bpf_helpers.h

@@ -51,7 +51,7 @@
 #endif
 
 #ifndef KERNEL_VERSION
-#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + ((c) > 255 ? 255 : (c))
+#define KERNEL_VERSION(a, b, c) (((a) << 16) + ((b) << 8) + ((c) > 255 ? 255 : (c)))
 #endif
 
 /*