bpf: btf: fix inconsistent IS_ERR and PTR_ERR

Fix inconsistent IS_ERR and PTR_ERR in get_btf,
the proper pointer to be passed as argument is '*btf'

This issue was detected with the help of Coccinelle.

Fixes: 2d3feca8c44f ("bpf: btf: print map dump and lookup with btf info")
Signed-off-by: YueHaibing <[e-mail]>
Acked-by: David S. Miller <[e-mail]>
Acked-by: Jakub Kicinski <[e-mail]>
Acked-by: Martin KaFai Lau <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>

tools/bpf/bpftool/map.c

···
 
 	*btf = btf__new((__u8 *)btf_info.btf, btf_info.btf_size, NULL);
 	if (IS_ERR(*btf)) {
-		err = PTR_ERR(btf);
+		err = PTR_ERR(*btf);
 		*btf = NULL;
 	}