PCI: stm32: Don't use 'proxy' headers

PCI: stm32: Don't use 'proxy' headers

Update header inclusions to follow IWYU (Include What You Use)
principle.

In particular, replace of_gpio.h, which is subject to removal by the
GPIOLIB subsystem, with the respective headers that are being used by the
driver.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20251114185534.3287497-1-andriy.shevchenko@linux.intel.com