media: staging: atomisp: convert timestamps to ktime_t

timespec overflows in 2038 on 32-bit architectures, and the
getnstimeofday() suffers from possible time jumps, so the
timestamps here are better done using ktime_get(), which has
neither of those problems.

In case of ov2680, we don't seem to use the timestamp at
all, so I just remove it.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>