MAINTAINERS: add myself for spi-bcm63xx

I noticed the driver is unclaimed. Since I was the last one doing
substantial work on it, add me as the maintainer.

As it is only found in legacy products, mark it as "Odd Fixes"
instead of "Maintained".

Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Acked-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20230708195309.72767-1-jonas.gorski@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>