PCI: rockchip-ep: Use a macro to define EP controller .align feature

Introduce the macro ROCKCHIP_PCIE_AT_SIZE_ALIGN to initialize the .align
field of the controller epc_features structure to 256. This is defined
as a shift using the macro ROCKCHIP_PCIE_AT_MIN_NUM_BITS (to avoid
using the "magic" value 8 directly).

Link: https://lore.kernel.org/r/20241017015849.190271-3-dlemoal@kernel.org


Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>