power: qpnp-fg-gen4: Switch to using TTF/TTE algorithms from fg-alg.c

Currently, Time to full (TTF) and Time to empty (TTE) algorithms
are supported in GEN4 FG driver locally. Since the algorithms are
moved to fg-alg.c to share it with QG driver, make changes to
GEN4 FG driver to switch using that.

Change-Id: I0059630c0ca0103b958ced10ae4bad8e1ccea8f7
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>