bpf: Move the declaration of __bpf_obj_drop_impl() to bpf.h

both syscall.c and helpers.c have the declaration of
__bpf_obj_drop_impl(), so just move it to a common header file.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20231020133202.4043247-6-houtao@huaweicloud.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

include/linux/bpf.h

@@ -2058,6 +2058,7 @@ struct btf_record *btf_record_dup(const struct btf_record *rec);
 bool btf_record_equal(const struct btf_record *rec_a, const struct btf_record *rec_b);
 void bpf_obj_free_timer(const struct btf_record *rec, void *obj);
 void bpf_obj_free_fields(const struct btf_record *rec, void *obj);
+void __bpf_obj_drop_impl(void *p, const struct btf_record *rec);
 
 struct bpf_map *bpf_map_get(u32 ufd);
 struct bpf_map *bpf_map_get_with_uref(u32 ufd);

kernel/bpf/helpers.c

@@ -1811,8 +1811,6 @@ bpf_base_func_proto(enum bpf_func_id func_id)
 	}
 }
 
-void __bpf_obj_drop_impl(void *p, const struct btf_record *rec);
-
 void bpf_list_head_free(const struct btf_field *field, void *list_head,
 			struct bpf_spin_lock *spin_lock)
 {

kernel/bpf/syscall.c

@@ -626,8 +626,6 @@ void bpf_obj_free_timer(const struct btf_record *rec, void *obj)
 	bpf_timer_cancel_and_free(obj + rec->timer_off);
 }
 
-extern void __bpf_obj_drop_impl(void *p, const struct btf_record *rec);
-
 void bpf_obj_free_fields(const struct btf_record *rec, void *obj)
 {
 	const struct btf_field *fields;