driver/max11871: add sysfs debug interface

driver/max11871: add sysfs debug interface

BZ: 32663

This patch add sysfs debug interface to
max11871 touchscreen driver.
The interfaces added includes command,
fw_ver, hreset, sreset, irq_count and
panel_params.

Signed-off-by: jli127 <jian.d.li@intel.com>
Change-Id: Ieabad396f23b2ee5868478c9f6f9b40360d4b9e0
Reviewed-on: http://android.intel.com:8080/45344
Reviewed-by: Koskinen, Ilkka <ilkka.koskinen@intel.com>
Reviewed-by: Du, Alek <alek.du@intel.com>
Tested-by: Wang, Zhifeng <zhifeng.wang@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>