media: vivid: print time in y2038-safe way

time_to_tm() takes a time_t value that overflows in 2038 on 32-bit
systems. time64_to_tm() doesn't have this problem, so let's use that in
combination with ktime_get_real_seconds() to read a 64-bit time
value.

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