During board initialization read the shared memory item
SMEM_POWER_ON_STATUS_INFO and place it in the procfs at
/proc/sys/kernel/boot_reason

The data item is an integer with a bit being set to identify the reason
the device was powered on. The values of this data item is defined in
the document Document/arm/msm/boot.txt, the following is the data in the
documentation file.

power_on_status values set by the PMIC for power on event:
----------------------------------------------------------
0x01 -- keyboard power on
0x02 -- RTC alarm
0x04 -- cable power on
0x08 -- SMPL
0x10 -- Watch Dog timeout
0x20 -- USB charger
0x40 -- Wall charger
0xFF -- error reading power_on_status value

Change-Id: I59e665f92e6e29f7dfef4380314f676a2d92c94b
Signed-off-by: Rick Adams <rgadams@codeaurora.org>