PCI: endpoint: pci-epf-test: Fix check for DMA MEMCPY test

PCI: endpoint: pci-epf-test: Fix check for DMA MEMCPY test

Currently, if DMA MEMCPY test is requested by the host, and if the endpoint
DMA controller supports DMA_PRIVATE, the test will fail. This is not
correct since there is no check for DMA_MEMCPY capability and the DMA
controller can support both DMA_PRIVATE and DMA_MEMCPY.

Fix the check and also reword the error message.

Link: https://lore.kernel.org/r/20250116171650.33585-2-manivannan.sadhasivam@linaro.org
Fixes: 8353813c88ef ("PCI: endpoint: Enable DMA tests for endpoints with DMA capabilities")
Reported-by: Niklas Cassel <cassel@kernel.org>
Closes: https://lore.kernel.org/linux-pci/Z3QtEihbiKIGogWA@ryzen
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Niklas Cassel <cassel@kernel.org>