pinctrl: samsung: Consistently use unsigned instead of u32 for nr_banks

Unlike for other countable members, the driver used u32 for number of
banks (nr_banks).  There is no specific need for using fixed-width
integer in this particular place.  Make it consistent.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>