ARM: dts: msm: Specify ADC channels for PM855B charger on SM8150

Specify VADC channels for PM855B charger device so that USB input
voltage, current and charger temperature can be read for SM8150
platforms.

CRs-Fixed: 2228622
Change-Id: I2e7291ea8cfce7cfc38a032aa92e70b07994906f
Signed-off-by: Harry Yang <harryy@codeaurora.org>
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>