boot_time is represented as a struct timespec.
struct timespec and CURRENT_TIME are not y2038 safe.
Overall, the plan is to use timespec64 and ktime_t for
all internal kernel representation of timestamps.
CURRENT_TIME will also be removed.
boot_time is used to construct the nfs client boot verifier.
Use ktime_t to represent boot_time and ktime_get_real() for
the boot_time value.
Following Trond's request https://lkml.org/lkml/2016/6/9/22 ,
use ktime_t instead of converting to struct timespec64.
Use higher and lower 32 bit parts of ktime_t for the boot
verifier.
Use the lower 32 bit part of ktime_t for the authsys_parms
stamp field.