PCI: endpoint: Use of_dma_configure() to set initial DMA mask

Use of_dma_configure() to set the initial DMA mask of EPF device. This
helps to get rid of "Coherent DMA mask 0x0 (pfn 0x0-0x1) covers a smaller
range of system memory than the DMA zone pfn" warning in certain platforms
like TI's K2G resulting in coherent DMA mask not being set.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>