V4L/DVB (5599): Use menuconfig objects II - DVB

Change Kconfig objects from "menu, config" into "menuconfig" so
that the user can disable the whole feature without having to
enter the menu first.
Also remove one indirection (CONFIG_DVB) that does not seem to
be really used inside the kernel.

Signed-off-by: Jan Engelhardt <jengelh@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>