perl: needs MMU

see build http://autobuild.buildroot.net/results/ba7/ba71d0d532ccd8e16b727cddd5dcaa5521074945/

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>