ipmi: Change to ktime_get_ts64()

getnstimeofday64() is deprecated because of the inconsistent naming,
it is only a wrapper around ktime_get_real_ts64() now, which could be
used as a direct replacement.

However, it is generally better to use CLOCK_MONOTONIC timestamps
where possible, to avoid glitches with a concurrent settimeofday()
or leap second.

The uses in ipmi are either for debugging prints or for comparing against
a prior timestamp, so using a monotonic ktime_get_ts64() is probably
best here.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Corey Minyard <cminyard@mvista.com>