gpio: sim: Use correct order for the parameters of devm_kcalloc()

We should have 'n', then 'size', not the opposite.
This is harmless because the 2 values are just multiplied, but having
the correct order silence a (unpublished yet) smatch warning.

Fixes: cb8c474e ("gpio: sim: new testing module")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>