pinctrl: bcm: fix kconfig dependency warning when !GPIOLIB

When PINCTRL_BCM2835 is enabled and GPIOLIB is disabled, it results in the
following Kbuild warning:

WARNING: unmet direct dependencies detected for GPIOLIB_IRQCHIP
  Depends on [n]: GPIOLIB [=n]
  Selected by [y]:
  - PINCTRL_BCM2835 [=y] && PINCTRL [=y] && OF [=y] && (ARCH_BCM2835 [=n] || ARCH_BRCMSTB [=n] || COMPILE_TEST [=y])

The reason is that PINCTRL_BCM2835 selects GPIOLIB_IRQCHIP without
depending on or selecting GPIOLIB while GPIOLIB_IRQCHIP is subordinate to
GPIOLIB.

Honor the kconfig menu hierarchy to remove kconfig dependency warnings.

Fixes: 85ae9e51

 ("pinctrl: bcm2835: switch to GPIOLIB_IRQCHIP")
Signed-off-by: Necip Fazil Yildiran <fazilyildiran@gmail.com>
Link: https://lore.kernel.org/r/20200914144025.371370-1-fazilyildiran@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>