clocksource/drivers/c-sky: fixup ftrace call-graph panic

We must add notrace on sched_clock_read, because it's called
by ftrace_graph_caller.

Signed-off-by: Guo Ren <ren_guo@c-sky.com>

clocksource/drivers/c-sky: fixup qemu fail to bootup sometimes.

Timer startup must after timer_irq_enable. For qemu, timer tick
irq hanppens but irq not enable, so it will cause qemu boot failed.

Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Tested-by: Liu Zhiwei <zhiwei_liu@c-sky.com>

clocksource/drivers/c-sky: Add C-SKY SMP timer

The driver is for C-SKY SMP timer. It only supports oneshot event
and 32bit overflow for clocksource. Per cpu core has one timer and
all timers share one clock-counter-input from the same clocksource.

This use mfcr&mtcr instructions to access the regs.

Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>