MAINTAINERS: Add nios2-related files to the Nios2 section

nios2_iic.c and the default-configs/nios2-softmmu.mak file are
currently "unmaintained" according to the get_maintainers.pl script.
Move them to the Nios2 section where they obviously belong to.
Signed-off-by: NThomas Huth <thuth@redhat.com>
Reviewed-by: NLaurent Vivier <laurent@vivier.eu>
Message-Id: <1542899500-23346-1-git-send-email-thuth@redhat.com>
Signed-off-by: NLaurent Vivier <laurent@vivier.eu>

MAINTAINERS

@@ -233,7 +233,9 @@ M: Marek Vasut <marex@denx.de>
 S: Maintained
 F: target/nios2/
 F: hw/nios2/
+F: hw/intc/nios2_iic.c
 F: disas/nios2.c
+F: default-configs/nios2-softmmu.mak
 
 OpenRISC
 M: Stafford Horne <shorne@gmail.com>