drivers: base: cpu: Add a knob to suppress cpu uevents

Provide an interface to suppress cpu uevents. This allows
uevents to be supressed during CPU hotplug. This is needed
for cases, where userspace wants to ignore processing CPU
sysfs nodes during CPU online notifications, for CPUs which
were online during coldboot, but were later hotplugged out,
and for which sysfs nodes were persistent across hotplug.

Change-Id: Ib88e61725fcf589adc195a637c00836ca9155afe
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>