PCI: dwc: dra7xx: Push request_irq() call to the bottom of probe

Currently devm_request_irq() is being called before base, PCI fields of
dra7xx_pcie structure are populated. It is called even before
pm_runtime_enable() and pm_runtime_get_sync() are called. This will lead
to exceptions if in case an interrupt is triggered before the all of the
above are done. Hence push the devm_request_irq() call to the end of the
probe.

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