media: v4l2-dv-timings.c: fix format string

It should be "%u.%02u" instead of "%u.%u".

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reported-by: Bard Winther <bwinther@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>