Wrong values of hfreq and image height can lead to strange timings.
Avoid timing calculations for such values.

Suggested By: Martin Bugge <marbugge@cisco.com>

Cc: Martin Bugge <marbugge@cisco.com>
Signed-off-by: NPrashant Laddha <prladdha@cisco.com>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>