MAINTAINERS: add Matthew Fortune for MIPS

MAINTAINERS

@@ -7,6 +7,9 @@ ARC:
 Alexey Brodkin <Alexey.Brodkin@synopsys.com>
 Vineet Gupta <Vineet.Gupta1@synopsys.com>
 
+MIPS:
+Matthew Fortune <Matthew.Fortune@imgtec.com>
+
 NDS32:
 Vincent Ren-Wei Chen <vincentc@andestech.com>
 Che-Wei Chuang <cnoize@andestech.com>