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: Thomas Huth <thuth@redhat.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <1542899500-23346-1-git-send-email-thuth@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>