MAINTAINERS: add polarfire soc reset controller

Add the newly added reset controller for the PolarFire SoC (MPFS) to
the existing MAINTAINERS entry.
Reviewed-by: Daire McNamara <daire.mcnamara@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220909123123.2699583-7-conor.dooley@microchip.com

MAINTAINERS

@@ -17532,6 +17532,7 @@ F:	drivers/char/hw_random/mpfs-rng.c
 F:	drivers/clk/microchip/clk-mpfs.c
 F:	drivers/mailbox/mailbox-mpfs.c
 F:	drivers/pci/controller/pcie-microchip-host.c
+F:	drivers/reset/reset-mpfs.c
 F:	drivers/rtc/rtc-mpfs.c
 F:	drivers/soc/microchip/
 F:	drivers/spi/spi-microchip-core.c