media: solo6x10: use ktime_get_ts64() for time sync

solo6x10 correctly deals with time stamps and will never
suffer from overflows, but it uses the deprecated 'struct timespec'
type and 'ktime_get_ts()' interface to read the monotonic clock.

This changes it to use ktime_get_ts64() instead, so we can
eventually remove ktime_get_ts().

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ismael Luceno <ismael@iodev.co.uk>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>