dt-bindings: qpnp-fg-gen4: Set defaults for {dis}charging Ki coefficients

Set default values for the low, medium, and high gain Ki coefficients
for both charging and discharging states.

Change-Id: I03a95089cacd78648af28c0e6c51f6571b7881b5
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>