selftests/bpf: Use BPF_PROG2 for some fentry programs without struct arguments

Use BPF_PROG2 instead of BPF_PROG for programs in progs/timer.c
to test BPF_PROG2 for cases without struct arguments.
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20220831152718.2081091-1-yhs@fb.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/progs/timer.c

@@ -120,7 +120,7 @@ static int timer_cb1(void *map, int *key, struct bpf_timer *timer)
 }
 
 SEC("fentry/bpf_fentry_test1")
-int BPF_PROG(test1, int a)
+int BPF_PROG2(test1, int, a)
 {
 	struct bpf_timer *arr_timer, *lru_timer;
 	struct elem init = {};
@@ -236,7 +236,7 @@ int bpf_timer_test(void)
 }
 
 SEC("fentry/bpf_fentry_test2")
-int BPF_PROG(test2, int a, int b)
+int BPF_PROG2(test2, int, a, int, b)
 {
 	struct hmap_elem init = {}, *val;
 	int key = HTAB, key_malloc = HTAB_MALLOC;