explicitly specify that offload.o & test.o bpf programs are S+

Note: due to the release version of the Connectivity/Tethering mainline
module being built from sc-mainline-prod, this won't actually take effect
until system/bpf bpfloader at version 0.6+ is merged in to that tree.

This doesn't really matter, since currently things default to v0.0+.
But there is no mainline module updatable pre-v0.2 supported OS
anyway. BpfLoader v0.2 is what shipped in Android S Beta 4 through
Android S Final.

Before S there simply was no bpfloader support for mainline updatable
ebpf code, while S Beta 3 and earlier shipped v0.0 which is badly
incompatible with even the current version of the mainline module.

Additionally v0.0 doesn't even parse this field, while v0.1 which
does was very short lived [~3 days] and can thus be utterly ignored.

As such this change is effectively a no-op, and even post merge
of bpfloader v0.6+ into sc-mainline-prod will still be effectively
a no-op.

So why do it? I want to explicitly document that these programs are S+,
so that I can change the default in the future to be T+.

Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I7e5d0124700c7045abe16b1f3b504c9e88054ff2

Tethering/bpf_progs/offload.c

@@ -24,6 +24,9 @@
 #define __kernel_udphdr udphdr
 #include <linux/udp.h>
 
+// The resulting .o needs to load on the Android S bpfloader v0.2
+#define BPFLOADER_MIN_VER 2u
+
 #include "bpf_helpers.h"
 #include "bpf_net_helpers.h"
 #include "bpf_tethering.h"

Tethering/bpf_progs/test.c

@@ -18,6 +18,9 @@
 #include <linux/in.h>
 #include <linux/ip.h>
 
+// The resulting .o needs to load on the Android S bpfloader v0.2
+#define BPFLOADER_MIN_VER 2u
+
 #include "bpf_helpers.h"
 #include "bpf_net_helpers.h"
 #include "bpf_tethering.h"