Linux_5.0: replace do_gettimeofday with ktime_get_real_ts64

Linux_5.0: replace do_gettimeofday with ktime_get_real_ts64

In Kernel commit e4b92b108c6cd6b311e4b6e85d6a87a34599a6e3 the
do_gettimeofday function was removed.

According to the Linux Documentation/core-api/timekeeping.rst
ktime_get_real_ts64 is the direct replacement for do_gettimeofday

Updated the macro osi_GetTime to use ktime_get_real_ts64 if it is
available.

Reviewed-on: https://gerrit.openafs.org/13433
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit b892fb127815bdf72103ae41ee70aadd87931b0c)

Change-Id: I1a0237457e229a11d2a87a3a269cf24adc201e59
Reviewed-on: https://gerrit.openafs.org/13441
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>