cris: arch-v32: gpio: Use kzalloc instead of kmalloc/memset

Turn a kmalloc/memset into an equivalent kzalloc.
Doing so also move the zero'ing of the memory outside of a mutex.

Signed-off-by: Christophe Jaillet <christophe.jaillet@wanadoo.fr>
Signed-off-by: Jesper Nilsson <jespern@axis.com>