MAINTAINERS: Update BNXT entry with firmware files

There appears to be a maintainer gap for BNXT TEE firmware files which
causes some patches to be missed. Update the entry for the BNXT Ethernet
controller with its companion firmware files.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Link: https://lore.kernel.org/r/20220427163606.126154-1-f.fainelli@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>