ARM: dts: add XOADC and IIO HWMON to MSM8660/APQ8060

This adds the PM8058 XOADC node to the PM8058 PMIC node,
defines the 16 channels and further also define an IIO HWMON
node for the channels that are used for housekeeping of
voltages and die temperature for the PMIC chip die.

Tested on the APQ8060 DragonBoard:
cd /sys/class/hwmon/hwmon0
cat in2_input
4773 (DC mains ~5V)
cat in4_input
625  (0.625V reference voltage)
cat in5_input
1250 (1.25V reference voltage)
cat temp1_input
35852 (die temperature)

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>