defconfig: sdm855: enable GEN4 FG driver

GEN4 FG driver adds support for fuel gauge that is present on
PM855B which will be used for gauging the battery on SDM855
platforms. Enable it.

Change-Id: I3f3013c554adff4608d852f4dadd0809c41d03fb
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>