PCI: endpoint: Improve pci_epf_alloc_space() API

PCI: endpoint: Improve pci_epf_alloc_space() API

pci_epf_alloc_space() already performs checks on the requested BAR size,
and will allocate and set epf_bar->size to a size higher than the
requested BAR size if some constraint deems it necessary.

However, there are additional checks done in the function drivers like
pci-epf-test.c, other than the existing checks in this API.

And similar checks are proposed to other endpoint function drivers, see:
https://lore.kernel.org/linux-pci/20240108151015.2030469-1-Frank.Li@nxp.com

Having these checks scattered over different locations in multiple EPF
drivers is not maintainable and makes the code hard to follow.

Since pci_epf_alloc_space() already performs roundups and some checks,
let's move the additional checks from pci-epf-test.c to
pci_epf_alloc_space().

This makes the API more robust and also offloads the checks from the
function drivers.

Signed-off-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20240207213922.1796533-3-cassel@kernel.org
[mani: reworded commit message and fixed uninitialized 'dev' pointer issue]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>