power: bcl: Add hotplug mitigation support

Add Support for hotplugging the CPU's when BCL
thresholds are reached.

The default mask indicating the cores to hotplug
on BCL conditions is defined in device tree.
BCL module provides a sysfs node to input and
read the current hotplug mask.
/qcom,bcl.#/hotplug_mask
Here the bits 0-7 corresponds to cores 0-7
respectively. If the value of the bit is set to 1,
then the corresponding core will be hotplugged on
battery current limit condition.

BCL module also provides another sysfs node,
/qcom,bcl.#/hotplug_status
which shows the current cores hotplugged
because of BCL conditions.

Change-Id: I4cc8e1da6ed77fcf3e03c0b925e427d2fc94aeca
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>