power: qcom-battery: Add sysfs to restrict charging

Add sysfs files for user applications to restrict
the battery charge current (FCC). The two files in
/sys/class/qcom-battery/ are -

1. restricted_charging: To enable/disable this feature
2. restricted_current: Restricted FCC (uA)

The default restricted_current value is 1A.

CRs-Fixed: 1113761
Change-Id: I23a6796eaa0c41c2e93a52c45f6200326d262e99
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>