PCI: brcmstb: Remove stale comment

A comment says that Multi-MSI is not supported by the driver.
A past commit [1] added this feature, so the comment is
incorrect and is removed.

[1] commit 198acab1 ("PCI: brcmstb: Enable Multi-MSI")

Link: https://lore.kernel.org/r/20230623144100.34196-6-james.quinlan@broadcom.com


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