ARM: dts: msm: configure APC supply regulator S2 to auto mode for msm8226

Configure PMIC PM8226 regulator SMPS 2 for auto mode.  When
operating in auto mode, the regulator automatically switches
between PWM (high power) and PFM (low power) modes based upon
real-time current consumption.  This results in lower aggregate
power consumption since PFM mode has lower ground current than
PWM mode.

Change-Id: I4868a965e033000a27d55db43f37140910eeba8b
CRs-Fixed: 522545
Signed-off-by: David Collins <collinsd@codeaurora.org>