MAINTAINERS: Add entry for Broadcom Broadband SoC HS SPI drivers

MAINTAINERS: Add entry for Broadcom Broadband SoC HS SPI drivers

The driver and device tree doc were originally authored by Jonas Gorski
and it has been updated from Broadcom recently including the dts yaml
file and a new driver for the updated controller. Add Jonas Gorski and
Broadcom engineers William Zhang and Kursad Oney as the maintainers.

Signed-off-by: William Zhang <william.zhang@broadcom.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20230209200246.141520-16-william.zhang@broadcom.com
Signed-off-by: Mark Brown <broonie@kernel.org>