Add a clocksource based on the goldfish-rtc device.
Move the timer register definition to <clocksource/timer-goldfish.h>
This kernel implementation is based on the QEMU upstream implementation:
https://git.qemu.org/?p=qemu.git;a=blob_plain;f=hw/rtc/goldfish_rtc.c
goldfish-timer is a high-precision signed 64-bit nanosecond timer.
It is part of the 'goldfish' virtual hardware platform used to run
some emulated Android systems under QEMU.
This timer only supports oneshot event.
Signed-off-by: Laurent Vivier <laurent@xxxxxxxxx>