PCI: microchip: Re-partition code between probe() and init()

Continuing to use pci_host_common_probe() for the PCIe Root Complex on
PolarFire SoC is leading to an extremely large _init() function and some
unnatural code flow. Re-partition the code so that some tasks are done
in a _probe() routine, which calls pci_host_common_probe() and then use
a much smaller _init() function, mainly to enable interrupts after
address translation tables are set up.

Link: https://lore.kernel.org/r/20230728131401.1615724-8-daire.mcnamara@microchip.com


Signed-off-by: Daire McNamara <daire.mcnamara@microchip.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>