V4L/DVB: remove unused #include <version.h>

The file(s) below do not use LINUX_VERSION_CODE nor KERNEL_VERSION.
  drivers/media/dvb/frontends/si21xx.c

This patch removes the said #include <version.h>.

Cc: Igor M. Liplianin <liplianin@tut.by>
Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>