[media] dvb-usb: remove another redundant #include <linux/kconfig.h>

Kernel source files need not include <linux/kconfig.h> explicitly
because the top Makefile forces to include it with:

  -include $(srctree)/include/linux/kconfig.h

Remove another reduntdant include, that managed to sneak by commit
97139d4a ("treewide: remove redundant #include <linux/kconfig.h>").

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>