hrtimer: Fix kernel-doc markups

The hrtimer_get_remaining() markup is documenting, instead,
__hrtimer_get_remaining(), as it is placed at the C file.

In order to properly document it, a kernel-doc markup is needed together
with the function prototype. So, add a new one, while preserving the
existing one, just fixing the function name.

The hrtimer_is_queued prototype has a typo: it is using
'=' instead of '-' to split: identifier - description
as required by kernel-doc markup.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/9dc87808c2fd07b7e050bafcd033c5ef05808fea.1605521731.git.mchehab+huawei@kernel.org