hinic: Use devm_kasprintf instead of hard coding it

'devm_kasprintf' is less verbose than:
   snprintf(NULL, 0, ...);
   devm_kzalloc(...);
   sprintf
so use it instead.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Zhao Chen <zhaochen6@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>