power: qpnp-smb2: Add support for reducing FCC for ESR

Use the CONSTANT_CURRENT property to reduce the FCC
for software based FG ESR.

Change-Id: I3284542f75cfa69ec4709d14688125e650cc8e09
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>