PCI: brcmstb: Enable Multi-MSI

We always wanted to enable Multi-MSI but didn't have a test device until
recently.  In addition, there are some devices out there that will ask for
multiple MSI but refuse to work if they are only granted one.

Link: https://lore.kernel.org/r/20221011184211.18128-2-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>