PCI: stm32: Add PCIe host support for STM32MP25

PCI: stm32: Add PCIe host support for STM32MP25

Add driver for the STM32MP25 SoC PCIe controller based on the DesignWare
PCIe core. Controller supports 2.5 and 5 GT/s data rates, MSI via GICv2m,
Single Virtual Channel, Single Function and WAKE# GPIO.

Signed-off-by: Christian Bruel <christian.bruel@foss.st.com>
[mani: reworded description]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
[bhelgaas: squash error handling cleanup from Christophe JAILLET
<christophe.jaillet@wanadoo.fr>:
https://patch.msgid.link/e69ade3edcec4da2d5bfc66e0d03bbcb5a857021.1759169956.git.christophe.jaillet@wanadoo.fr]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20250820075411.1178729-5-christian.bruel@foss.st.com