drivers: base: add cpu_device_create to support per-cpu devices

This patch adds a new function to create per-cpu devices.
This helps in:
1. reusing the device infrastructure to create any cpu related
   attributes and corresponding sysfs instead of creating and
   dealing with raw kobjects directly
2. retaining the legacy path(/sys/devices/system/cpu/..) to support
   existing sysfs ABI
3. avoiding to create links in the bus directory pointing to the
   device as there would be per-cpu instance of these devices with
   the same name since dev->bus is not populated to cpu_sysbus on
   purpose

Change-Id: I21a806635ca296f63bc0abae37c959f79a797339
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Git-commit: 3d52943b3a51497a777e6d7d840a38596a92cee9
Git-repo: https://source.codeaurora.org/quic/la/kernel/msm-4.9


Signed-off-by: Teng Fei Fan <tengfei@codeaurora.org>