Linux 5.0: implicit declaration of function current_kernel_time64

[tonyhutter]

System information

Type	Version/Name
Distribution Name	Fedora
Distribution Version	30 (rawhide)
Linux Kernel	5.0.0-0.rc1.git0.1.fc30.x86_64
Architecture	x86-64
ZFS Version	master
SPL Version	master

Describe the problem you're observing

current_kernel_time64() was removed from recent kernels. Looks like ktime_get_coarse_real_ts64() should be used instead.
https://lkml.org/lkml/2018/7/11/202
https://lkml.org/lkml/2018/12/17/110

Describe how to reproduce the problem

Build master in rawhide

Include any warning/errors/backtraces from the system logs

In file included from /home/hutter/zfs/include/spl/sys/condvar.h:33,
                 from /home/hutter/zfs/include/sys/zfs_context.h:38,
                 from /home/hutter/zfs/include/sys/crypto/common.h:39,
                 from /home/hutter/zfs/module/icp/illumos-crypto.c:35:
/home/hutter/zfs/include/spl/sys/time.h: In function ‘gethrestime’:
/home/hutter/zfs/include/spl/sys/time.h:76:8: error: implicit declaration of function ‘current_kernel_time64’; did you mean ‘core_kernel_text’? [-Werror=implicit-function-declaration]
  *ts = current_kernel_time64();
        ^~~~~~~~~~~~~~~~~~~~~
        core_kernel_text
/home/hutter/zfs/include/spl/sys/time.h:76:6: error: incompatible types when assigning to type ‘inode_timespec_t’ {aka ‘struct timespec64’} from type ‘int’
  *ts = current_kernel_time64();
      ^
/home/hutter/zfs/include/spl/sys/time.h: In function ‘gethrestime_sec’:
/home/hutter/zfs/include/spl/sys/time.h:86:24: error: invalid initializer
  inode_timespec_t ts = current_kernel_time64();
                        ^~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

[Hubbitus]

Looks related to https://lore.kernel.org/patchwork/patch/562186/