Staging: olpc_dcon: Replace timespec with ktime_t

Struct timespec will overflow in year 2038, here it will not cause an
overflow because it is used with timespec_sub, but still has to be
removed as part of y2038 changes. Replace it with ktime_t. Also use
monotonic instead of real-time by replacing functions getnstimeofday
with ktime_get.

Signed-off-by: Ksenija Stanojevic <ksenija.stanojevic@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>