This patch changes 32-bit time types to 64-bit in
drivers/power/ab8500_fg.c
timespec and time_t can only represent signed 32-bit
dates but the driver should represent dates that are
after January 2038. So used time64.h header file and
its proper types and functions.
Use time64_t type instead of __kernel_time_t for
time_stamps variable of ab8500_fg_avg_cap struct