power: qpnp-fg-gen4: Initialize SOH to -EINVAL

Similar to QG driver, initialize SOH to -EINVAL so that the user
can interpret it the same way before SOH algorithm writes back
calculated SOH to bms power supply.

Change-Id: I424e18709050b5b930214bfe69c1cf105539000c
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>