MAINTAINERS: add qspi to Polarfire SoC entry

Add the qspi driver to existing Polarfire SoC entry.
Signed-off-by: Naga Sureshkumar Relli <nagasuresh.relli@microchip.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220808064603.1174906-5-nagasuresh.relli@microchip.comSigned-off-by: Mark Brown <broonie@kernel.org>

MAINTAINERS

@@ -17534,6 +17534,7 @@ F:	drivers/mailbox/mailbox-mpfs.c
 F:	drivers/pci/controller/pcie-microchip-host.c
 F:	drivers/rtc/rtc-mpfs.c
 F:	drivers/soc/microchip/
+F:	drivers/spi/spi-microchip-core-qspi.c
 F:	drivers/spi/spi-microchip-core.c
 F:	drivers/usb/musb/mpfs.c
 F:	include/soc/microchip/mpfs.h