bpf: Export bpf_base_func_proto

The bpf_testmod needs to use the bpf_tail_call helper in
a later selftest patch. This patch is to EXPORT_GPL_SYMBOL
the bpf_base_func_proto.

Signed-off-by: Martin KaFai Lau <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

kernel/bpf/helpers.c

···
 		return NULL;
 	}
 }
+EXPORT_SYMBOL_GPL(bpf_base_func_proto);
 
 void bpf_list_head_free(const struct btf_field *field, void *list_head,
 			struct bpf_spin_lock *spin_lock)