Currently all OSTM devices are called "ostm", also in kernel messages.

As there can be multiple instances in an SoC, this can confuse the user.
Hence construct a unique name from the DT node name, like is done for
platform devices.

On RSK+RZA1, the boot log changes like:

    -clocksource: ostm: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 57352151442 ns
    +clocksource: timer@fcfec000: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 57352151442 ns
     sched_clock: 32 bits at 33MHz, resolution 30ns, wraps every 64440619504ns
    -ostm: used for clocksource
    -ostm: used for clock events
    +/soc/timer@fcfec000: used for clocksource
    +/soc/timer@fcfec400: used for clock events
     ...
    -clocksource: Switched to clocksource ostm
    +clocksource: Switched to clocksource timer@fcfec000
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20191016144747.29538-5-geert+renesas@glider.be