PCI: brcmstb: Replace status loops with read_poll_timeout_atomic()

It would be nice to replace the PCIe link-up loop as well but
there are too many uses of this that do not poll (and the
read_poll_timeout uses "timeout==0" to loop forever).

Link: https://lore.kernel.org/r/20221011184211.18128-4-jim2101024@gmail.com


Signed-off-by: Jim Quinlan <jim2101024@gmail.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>