ARM: dts: msm: add I2C buck regulator devices for msm8939

Add I2C controlled buck regulator devices which provide voltage for
msm8939 APC power rail. Onsemi NCP6335D and Fairchild FAN53555 are both
supported on msm8939 boards.

Change-Id: I2acc664456ceb89c62c10ff2eb01f27f939d2e5b
Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>