PCI: qcom-ep: Add eDMA support

Qualcomm PCIe Endpoint controllers have the in-built Embedded DMA (eDMA)
peripheral for offloading the data transfer between PCIe bus and memory.

Let's add the support for it by enabling the eDMA IRQ in the driver.
Rest of the functionality will be handled by the eDMA DMA Engine driver.

Since the eDMA on Qualcomm platforms only uses a single IRQ for all
channels, use 1 for edma.nr_irqs.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>