power: qpnp-charger: add disable adc disable work

The ADC channel disable API may sleep when it is called. Move
the call to a work to avoid a kernel bug.

Change-Id: I75771c6b8219c0e8226083d5dce66c51c4a7624b
Signed-off-by: David Keitel <dkeitel@codeaurora.org>