power: bcl_peripheral: Fix Ibat calculation

Fix Ibat calculation. This is required since Ibat
reading is showing high values even when the current
is low. This will lead to unnecessary mitigation.

Change-Id: I1b1442d1576675d6eb7aafbcd8767d95b48feff2
Signed-off-by: Shiju Mathew <shijum@codeaurora.org>