selftests/bpf/test_offload.py: Fix expected case of extack messages

Commit 7f0a838 ("bpf, xdp: Maintain info on attached XDP BPF programs
in net_device") changed the case of some of the extack messages being
returned when attaching of XDP programs failed. This broke test_offload.py,
so let's fix the test to reflect this.

Fixes: 7f0a838 ("bpf, xdp: Maintain info on attached XDP BPF programs in net_device")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/bpf/160752226175.110217.11214100824416344952.stgit@toke.dk

Author: tohojo

tools/testing/selftests/bpf/test_offload.py

@@ -1004,7 +1004,7 @@ def test_multi_prog(simdev, sim, obj, modename, modeid):
                               fail=False, include_stderr=True)
     fail(ret == 0, "Replaced XDP program with a program in different mode")
     check_extack(err,
-                 "native and generic XDP can't be active at the same time.",
+                 "Native and generic XDP can't be active at the same time.",
                  args)
 
     start_test("Test MTU restrictions...")
@@ -1035,7 +1035,7 @@ def test_multi_prog(simdev, sim, obj, modename, modeid):
     offload = bpf_pinned("/sys/fs/bpf/offload")
     ret, _, err = sim.set_xdp(offload, "drv", fail=False, include_stderr=True)
     fail(ret == 0, "attached offloaded XDP program to drv")
-    check_extack(err, "using device-bound program without HW_MODE flag is not supported.", args)
+    check_extack(err, "Using device-bound program without HW_MODE flag is not supported.", args)
     rm("/sys/fs/bpf/offload")
     sim.wait_for_flush()