PCI: endpoint: test: Use pci_epc_mem_map/unmap()

Modify the endpoint test driver to use the functions pci_epc_mem_map()
and pci_epc_mem_unmap() for the read, write and copy tests. For each
test case, the transfer (dma or mmio) are executed in a loop to ensure
that potentially partial mappings returned by pci_epc_mem_map() are
correctly handled.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20241012113246.95634-6-dlemoal@kernel.org
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Author: damien-lemoal