staging: fsl-dpaa2/rtc: add rtc driver

This patch is to add driver for the DPAA2 1588 timer module (RTC)
which interfaces to up to an unlimited number of 10/100/1000 or
10G ethernet MACs, providing current time, alarm, and fiper support.
The 1588 IP control block includes these distinctive features.

- External GPIO trigger for time-stamping
- 2 Time-stamp alarms
- 3 FIPER pulse generators
- Phase adjusted output timer clock

Currently this driver only supports basic functions like
settime/gettime/adjtime/adjfreq.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>