PCI: brcmstb: Split brcm_pcie_setup() into two funcs

PCI: brcmstb: Split brcm_pcie_setup() into two funcs

We need to take some code in brcm_pcie_setup() and put it in a new function
brcm_pcie_linkup().  In future commits the brcm_pcie_linkup() function will
be called indirectly by pci_host_probe() as opposed to the host driver
invoking it directly.

Some code that was executed after the PCIe linkup is now placed so that it
executes prior to linkup, since this code has to run prior to the
invocation of pci_host_probe().

Link: https://lore.kernel.org/r/20220106160332.2143-5-jim2101024@gmail.com
Signed-off-by: Jim Quinlan <jim2101024@gmail.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>