power: fg-util: Notify FCC and FV to charger only if they're valid

Float voltage (FV) and Fast charging current (FCC) for a battery
is specified under the battery profile device tree. This is read
by the FG driver and notified to the charger driver. If these
parameters are not specified, then they're initialized to -EINVAL
currently. Do not notify these negative numbers to charger driver
which can affect charging parameters.

CRs-Fixed: 2306551
Change-Id: Ib7f6a941a264f154786ef239c6d02a7f8e0fcded
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>