MAINTAINERS: at91: Collect all pinctrl/gpio drivers in same entry

Andrei's address is not valid anymore, collect all pinctrl/gpio
entries in the common "PIN CONTROLLER - MICROCHIP AT91" one
and remove the PIOBU specific one.

Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20190823083158.2649-1-nicolas.ferre@microchip.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>