screen: fix parallel build

comm.h is needed to build list_display.o and list_generic.o otherwise
parallel builds will sometimes fail

Fixes:
 - http://autobuild.buildroot.org/results/43105f14857dbe72d8878fc7b3db67f7bdca93cc
 - http://autobuild.buildroot.org/results/47f4ecbec1355285633df287fc9c4e7cccde9378



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>