package/qt5serialbus: fix build with kernel >= 5.2

Fixes:
 - http://autobuild.buildroot.org/results/ddacee1d09f34fc718ef05a6e4f0bbbe26cd56d1
 - http://autobuild.buildroot.org/results/34a4ed20705b581add96fb5d97828909cee9015c



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