selftests/bpf: Remove enum64 case from __arg_untrusted test suite

The enum64 type used by verifier_global_ptr_args test case requires
CONFIG_SCHED_CLASS_EXT. At the moment selftets do not depend on this
option. There are just a few enum64 types in the kernel. Instead of
tying selftests to implementation details of unrelated sub-systems,
just remove enum64 test case. Simple enums are covered and that should
be sufficient.

Fixes: 68cca81fd57f ("selftests/bpf: tests for __arg_untrusted void * global func params")
Reported-by: Amery Hung <[e-mail]>
Signed-off-by: Eduard Zingerman <[e-mail]>
Tested-by: Amery Hung <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

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

···
 	return *(int *)p;
 }
 
-__weak int subprog_enum64_untrusted(enum scx_public_consts *p __arg_untrusted)
-{
-	return *(int *)p;
-}
-
 SEC("tp_btf/sys_enter")
 __success
 __log_level(2)
···
 	subprog_void_untrusted((void *)mem + off);
 	/* variable offset to untrusted mem (trusted) */
 	subprog_void_untrusted(bpf_get_current_task_btf() + off);
-	/* variable offset to untrusted char/enum/enum64 (map) */
+	/* variable offset to untrusted char/enum (map) */
 	subprog_char_untrusted(mem + off);
 	subprog_enum_untrusted((void *)mem + off);
-	subprog_enum64_untrusted((void *)mem + off);
 	return 0;
 }