PCI: imx6: Convert to use agnostic GPIO API

PCI: imx6: Convert to use agnostic GPIO API

The of_gpio.h legacy API is going to be removed. In preparation for that,
convert the driver to the agnostic API.

[kwilczynski: commit log]
Link: https://lore.kernel.org/linux-pci/20240506142142.4042810-5-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>