time: Add missing colons for parameter documentation of time64_to_tm()

Address these kernel-doc warnings:

 kernel/time/timeconv.c:79: warning: Function parameter or member
 'totalsecs' not described in 'time64_to_tm'
 kernel/time/timeconv.c:79: warning: Function parameter or member
 'offset' not described in 'time64_to_tm'
 kernel/time/timeconv.c:79: warning: Function parameter or member
 'result' not described in 'time64_to_tm'

The parameters are described but lack colons after the parameter name.

[ tglx: Massaged changelog ]

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1605252275-63652-1-git-send-email-alex.shi@linux.alibaba.com