ARM: imx: fix sync issue between imx_cpu_die and imx_cpu_kill

ARM: imx: fix sync issue between imx_cpu_die and imx_cpu_kill

There is a sync issue with hotplug operation.  It's possible that when
imx_cpu_kill gets running on primary core, the imx_cpu_die execution
on the core which is to be killed hasn't been finished yet.  The problem
will very likely be hit when running suspend without no_console_suspend
setting on kernel cmdline.

It uses cpu jumping argument register to sync imx_cpu_die and
imx_cpu_kill.  The register will be set in imx_cpu_die and imx_cpu_kill
will wait for the register being cleared to actually kill the cpu.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Cc: <stable@vger.kernel.org>