hwmon: qpnp-vadc: Set peripheral warm reset

It is seen on certain conditions during bootup the end
of conversion interrupt is latched and this causes the
VADC to never receive the end of conversion interrupt.
This causes the clients to experience delays when requesting
an ADC request and on certain scenario during a soft reset
condition delays bootup.

qpnp-int expects the peripheral interrupt registers to be
in a known state. If an interrupt occured and is not
handled correctly it could lead to the interrupt being
latched and subsequent interrupts are never handled.

Each qpnp peripheral has an option to reset the peripheral
when a warm reset occurs to reset the peripheral to its
power on reset state. Set the VADC peripheral reset register
to enable resetting the peripheral during a warm reset.

Change-Id: Ic59726d327bf93900011d6f7051b2967ed0eae87
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>