utils/genrandconfig: handle a10disp

a10disp will raise the following build failure with a mainline kernel:

cp: cannot stat '/home/autobuild/autobuild/instance-0/output-1/build/linux-5.17.15/include/video/sunxi_disp_ioctl.h': No such file or directory

Fixes:
 - http://autobuild.buildroot.org/results/1f2607d6adece4d5dfe17fbdb032a2d228fc030f



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