media: dvb-usb/cxusb-analog.c: fix coccinelle warning, use ktime.h

This patch fixes a coccinelle warning and includes ktime.h instead of
timekeeping.h. The first includes the latter, but the latter doesn't
exist before 3.17, causing problems for our compat build. It's easier
to just use ktime.h instead.

coccinelle warnings: (new ones prefixed by >>)

>> drivers/media/usb/dvb-usb/cxusb-analog.c:1498:41-42: WARNING: Use ARRAY_SIZE

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>