[ Upstream commit 1b4c794fda583edabe864ac466e9cd43c707be80 ]

Use rtc_add_group to add the common sysfs group to avoid a possible race
condition.

[Denis.Osterland@diehl.com: use to_i2c_client(dev->parent)]
Signed-off-by: NDenis Osterland <Denis.Osterland@diehl.com>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@bootlin.com>

The move of atrim, dtrim usr sysfs properties from i2c device
to rtc device require to access them via dev->parent.
This patch also aligns timestamp0.
Signed-off-by: NSasha Levin <sashal@kernel.org>