power: qpnp-fg-gen4: Modify Full SoC Ki coefficients

Change default values of Full SoC Ki coefficients to 40 (decimal) when
they are not specified via device tree, and also set them to zero while
discharging.

Change-Id: Ibc98a67e8d4da2c2ea3f3b48ef43e0497b55842f
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>