qcom: battery: Modify FCC split logic to use slave's limit

Currently, the parallel (slave) charger's share of FCC is limited by
only the BCL. Since SMB1354 can only supply a max of 2.5A FCC, this can
result in a "loss" of current in situations where it is allocated > 2.5A
of current as a result of the existing FCC split logic.

For example, if the SMB1354 is allocated 3A, the total FCC (main +
charger) will be short by 0.5A (3 - 2.5) because of the charger's FCC
limit.

Therefore, modify FCC split logic to use the parallel charger's FCC
limit to further restrict parallel's portion of FCC. This will ensure
that any current that exceeds 2.5A will be part of the main's share.

CRs-Fixed: 2170280
Change-Id: I01cd13d509a37963370c4dc2c815500fd1e821b9
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>