bpf: btf: Remove unused btf_field_info_type enum

This enum was added and used in commit aa3496ac ("bpf: Refactor kptr_off_tab
into btf_record"). Later refactoring in commit db559117 ("bpf: Consolidate
spin_lock, timer management into btf_record") resulted in the enum
values no longer being used anywhere.

Let's remove them.
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20230309180111.1618459-3-davemarchevsky@fb.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/btf.c

@@ -3231,12 +3231,6 @@ static void btf_struct_log(struct btf_verifier_env *env,
 	btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
 }
 
-enum btf_field_info_type {
-	BTF_FIELD_SPIN_LOCK,
-	BTF_FIELD_TIMER,
-	BTF_FIELD_KPTR,
-};
-
 enum {
 	BTF_FIELD_IGNORE = 0,
 	BTF_FIELD_FOUND  = 1,