[media] Staging: media: lirc: Replace timeval with ktime_t

'struct timeval last_tv' is used to get the time of last signal change
and 'struct timeval last_intr_tv' is used to get the time of last UART
interrupt.
32-bit systems using 'struct timeval' will break in the year 2038, so we
have to replace that code with more appropriate types.
Here struct timeval is replaced with ktime_t.

Signed-off-by: Ksenija Stanojevic <ksenija.stanojevic@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>