PCI: endpoint: Add pci_epf_get_required_bar_size() helper

PCI: endpoint: Add pci_epf_get_required_bar_size() helper

Introduce pci_epf_get_required_bar_size() helper to get the required BAR
size and backing memory size. This helper will be used to set a fixed MMIO
address as the backing memory for a BAR.

Since this helper returns both BAR size and the aligned memory size, use
two parameters, 'bar_size' and 'aligned_mem_size' to avoid confusion.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
[mani: renamed helper to pci_epf_get_required_bar_size(), reworded description]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Niklas Cassel <cassel@kernel.org>
Link: https://patch.msgid.link/20251015-vntb_msi_doorbell-v6-2-9230298b1910@nxp.com