scsi: 3ware: use 64-bit times for FW time sync

The calculation of the number of seconds since Sunday 00:00:00 overflows
in 2106, meaning that we instead will return the seconds since Wednesday
06:28:16 afterwards.

Using 64-bit time stamps avoids this slight inconsistency, and the
deprecated do_gettimeofday(), replacing it with the simpler
ktime_get_real_seconds().

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Adam Radford <aradford@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>