pinctrl: single: check for any error when getting rows

pinctrl_count_index_with_args returns -ENOENT not
-EINVAL. The return check would pass, and we would
try to kzalloc with a negative error size throwing
a warning.

Instead of checking for -EINVAL specifically, lets
check for any error and avoid negative size allocations.

Signed-off-by: Axel Haslam <ahaslam@baylibre.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>