PCI: stm32: Fix EP page_size alignment

PCI: stm32: Fix EP page_size alignment

pci_epc_mem_alloc_addr() allocates a CPU address from the ATU window phys
base and a page number. Set the ep->page_size so the resulting CPU address
is correctly aligned with the ATU required alignment.

Fixes: 151f3d29baf4 ("PCI: stm32-ep: Add PCIe Endpoint support for STM32MP25")
Signed-off-by: Christian Bruel <christian.bruel@foss.st.com>
[mani: added fixes tag]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20251114-atu_align_ep-v1-1-88da5366fa04@foss.st.com