power: qpnp-bms: Expose the learnt FCC values to userspace

The learnt FCC values need to be backed-up and restored
across reboot. Expose the FCC parameters to the userspace
via sysfs entries to facilitate this. Use sysfs_notify
to indicate a newly generated FCC value.

While at it, add CYCLE_COUNT property to expose the current
charge cycle.

Change-Id: I0fc62e0a3eea88cc082bec3ce4d1bc302be9ace1
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>