bpf: update the comment for BTF_FIELDS_MAX

The commit d56b63cf0c0f ("bpf: add support for bpf_wq user type")
changes the fields support number to 11, just sync the comment.

Signed-off-by: Haiyue Wang <[e-mail]>
Acked-by: Yonghong Song <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

include/linux/bpf.h

···
 };
 
 enum {
-	/* Support at most 10 fields in a BTF type */
+	/* Support at most 11 fields in a BTF type */
 	BTF_FIELDS_MAX	   = 11,
 };