firewire: use 64-bit time_t based interfaces

32-bit CLOCK_REALTIME timestamps overflow in year 2038, so all such
interfaces are deprecated now.  For the FW_CDEV_IOC_GET_CYCLE_TIMER2
ioctl, we already support 64-bit timestamps, but the implementation
still uses timespec.

This changes the code to use timespec64 instead with the appropriate
accessor functions.

Link: http://lkml.kernel.org/r/20180711124456.1023039-1-arnd@arndb.de


Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>