ARM: mach-imx: convert logical CPU numbers to physical numbers

This patch uses the new cpu_logical_map() macro for converting logical
CPU numbers into physical numbers when releasing CPUs during the SMP
boot and CPU hotplug paths.

Cc: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>