pinctrl: samsung: Fix pinctrl bank pin count

Commit 1abd18d1 ("pinctrl: samsung: Register pinctrl before GPIO")
changes the order of GPIO and pinctrl registration: now pinctrl is
registered before GPIO. That means gpio_chip->ngpio is not set when
samsung_pinctrl_register() called, and one cannot rely on that value
anymore. Use `pin_bank->nr_pins' instead of `pin_bank->gpio_chip.ngpio'
to fix mentioned inconsistency.

Fixes: 1abd18d1

 ("pinctrl: samsung: Register pinctrl before GPIO")
Signed-off-by: Jaehyoung Choi <jkkkkk.choi@samsung.com>
Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Link: https://lore.kernel.org/r/20210730192905.7173-1-semen.protsenko@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>