pinctrl/nomadik: allow to support several ranges per GPIO bank

With DB8500 the number of GPIO chips = number GPIO bank =
number of GPIO ranges.

With DB8540, a new GPIO range configuration is used, some GPIO
banks can have several GPIO ranges.

For example, DB8540 GPIO bank0 (GPIO0 to GPIO32) have 2 GPIO
ranges:
    - GPIO0 to GPIO17  : routed
    - GPIO18 to GPIO21 : hole
    - GPIO22 to GPIO28 : routed
    - GPIO29 to GPIO32 : hole

Previously, during nmk_pinctrl_probe(), all GPIO ranges were
parsed, as GPIO ranges are larger than the number of GPIO chips,
a warning occurs. This commit allows each bank to have several
GPIO ranges.

Signed-off-by: Patrice Chotard <patrice.chotard@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>