PCI: microchip: Move IRQ functions to pcie-plda-host.c

Move IRQ related functions to common file pcie-plda-host.c

The re-use code including MSI, INTx, event interrupts and IRQ init
functions.

Link: https://lore.kernel.org/linux-pci/[email protected]
Signed-off-by: Minda Chen <[email protected]>
Signed-off-by: Krzysztof Wilczyński <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>
Acked-by: Conor Dooley <[email protected]>

Author: mindachen1987