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: 8353813 ("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>

Author: Mani-Sadhasivam

drivers/pci/endpoint/functions/pci-epf-test.c

@@ -328,8 +328,8 @@ static void pci_epf_test_copy(struct pci_epf_test *epf_test,
 	void *copy_buf = NULL, *buf;
 
 	if (reg->flags & FLAG_USE_DMA) {
-		if (epf_test->dma_private) {
-			dev_err(dev, "Cannot transfer data using DMA\n");
+		if (!dma_has_cap(DMA_MEMCPY, epf_test->dma_chan_tx->device->cap_mask)) {
+			dev_err(dev, "DMA controller doesn't support MEMCPY\n");
 			ret = -EINVAL;
 			goto set_status;
 		}