drivers: qcom: Add SoC sleep stats driver

Qualcomm Technologies Inc's (QTI) chipsets support SoC level
low power modes. Statistics for SoC sleep stats are produced
by remote processor.

Lets's add a driver to read the shared memory exported by the
remote processor and export to sysfs.

Change-Id: I48d27380c0ecd22d5b35da39f3ed8baf2fa1aeef
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>
Signed-off-by: Lina Iyer <ilina@codeaurora.org>
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>