power: qpnp-fg-gen4: Fix esr_delta bounding error

During ESR calibration, a bounded function of esr_delta mistakenly
returns upper or lower bound, which eventually leads to large SOC
inaccuracy.

Fix it.

CRs-Fixed: 2282679
Change-Id: I70096b56c4b862cd9abf22aa799c952fb916d1d5
Signed-off-by: Harry Yang <harryy@codeaurora.org>