OST is the OS Timer, a 64-bit timer/counter with buffered reading.

SoCs before the JZ4770 had (if any) a 32-bit OST; the JZ4770 and
JZ4780 have a 64-bit OST.

This driver will register both a clocksource and a sched_clock to the
system.
Signed-off-by: NMaarten ter Huurne <maarten@treewalker.org>
Signed-off-by: NPaul Cercueil <paul@crapouillou.net>
Tested-by: NMathieu Malaterre <malat@debian.org>
Tested-by: NArtur Rojek <contact@artur-rojek.eu>
Signed-off-by: NDaniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200212180408.30872-1-paul@crapouillou.net