staging: greybus: MAINTAINERS: add greybus protocol drivers maintainers

Add me to some Greybus protocol drivers maintainers, spi, sdio, power
supply, light and gpio.

Signed-off-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>