Migrate fsl_ftm driver to the new 'set-state' interface provided by
clockevents core, the earlier 'set-mode' interface is marked obsolete
now.

This also enables us to implement callbacks for new states of clockevent
devices, for example: ONESHOT_STOPPED.

Cc: Xiubo Li <Li.Xiubo@freescale.com>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NDaniel Lezcano <daniel.lezcano@linaro.org>

The Freescale FlexTimer Module time reference is a 16-bit counter
that can be used as an unsigned or signed increase counter.

CNTIN defines the starting value of the count and MOD defines the
final value of the count. The value of CNTIN is loaded into the FTM
counter, and the counter increments until the value of MOD is reached,
at which point the counter is reloaded with the value of CNTIN. That's
also when an overflow interrupt will be generated.

Here using the 'evt' prefix or postfix as clock event device and
the 'src' as clock source device.
Signed-off-by: NXiubo Li <Li.Xiubo@freescale.com>
Cc: Shawn Guo <shawn.guo@linaro.org>
Cc: Jingchang Lu <b35083@freescale.com>
Signed-off-by: NDaniel Lezcano <daniel.lezcano@linaro.org>