PCI: endpoint: pci-epf-test: Simplify pci_epf_test_alloc_space() loop

PCI: endpoint: pci-epf-test: Simplify pci_epf_test_alloc_space() loop

Make pci-epf-test use pci_epc_get_next_free_bar() just like pci-epf-ntb.c
and pci-epf-vntb.c.

Using pci_epc_get_next_free_bar() also makes it more obvious that
pci-epf-test does no special configuration at all.

(The only configuration pci-epf-test does is setting
PCI_BASE_ADDRESS_MEM_TYPE_64 if epc_features has marked the specific BAR
as only_64bit. pci_epc_get_next_free_bar() already takes only_64bit into
account when looping.)

This way, the code is more consistent between EPF drivers, and pci-epf-test
does not need to explicitly check if the BAR is reserved, or if the index
belongs to a BAR succeeding a 64-bit only BAR.

Link: https://lore.kernel.org/linux-pci/20240320113157.322695-2-cassel@kernel.org
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>