Xilinx: ARM: Skip delay calibration in hotplug path

Changing the CPU frequency while one core is offline
taints the offline CPU's loops per jiffy value.
With this patch delay calibration is skipped when returning
from hotplug and the correct lpj value from the master CPU
is used.

This change is the same as commit
a279561879a795966336fb78186ee7435b6bb050 in
https://github.com/jcrigby/linaro-ci-kernels.git

.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>