power: qpnp-fg: fix address used of IADC gain compensation

When IADC gain compensation is enabled, gain value should
be stored in SRAM register 0x425 as specified in the
documentation. Fix SRAM register address to 0x425 in gain
reset condition.

CRs-Fixed: 886608
Change-Id: I56aa48d3b7e2960fc9f1afd8534d93c34b982114
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>