MAINTAINERS: add Microchip PolarFire FPGA drivers entry

MAINTAINERS: add Microchip PolarFire FPGA drivers entry

Add MAINTAINERS entry for the newly added Microchip PolarFire (MPF) FPGA
manager. Add myself as a reviewer and Conor Dooley as a maintainer.

Suggested-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Ivan Bornyakov <i.bornyakov@metrotek.ru>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Xu Yilun <yilun.xu@intel.com>
Link: https://lore.kernel.org/r/20220623163248.3672-6-i.bornyakov@metrotek.ru
Signed-off-by: Xu Yilun <yilun.xu@intel.com>