power: qpnp-charger: change VIN_MIN_MV to correct value

The VIN_MIN_MV value of 3.4 V is incorrect.

Fix this by setting it to the correct value of 4.2 V

Change-Id: I022f094a4bf890d1c28a23e382a7a72e9e8424f1
Signed-off-by: David Keitel <dkeitel@codeaurora.org>