PCI: xilinx: Removing struct hw_irq and adding generic PCI core API's

PCI: xilinx: Removing struct hw_irq and adding generic PCI core API's

ARM PCI architecture is getting updated to generic API's, independent
of ARM, ARM64. Removing architecure dependecy structure struct hw_irq
which is ARM 32-bit specific structure, and adding generic PCI core
API's to register to PCI subsystem.
Removing funtions which are not being used with generic API's.

Signed-off-by: Bharat Kumar Gogada <bharatku@xilinx.com>
Signed-off-by: Ravi Kiran Gummaluri <rgummal@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>