media: mxl5xx: remove unused including <linux/version.h>

Fix the following versioncheck warning:

drivers/media/dvb-frontends/mxl5xx.c:30:1: unused including
<linux/version.h>

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>