power: qpnp-bms: Avoid deadlock in reset_vbat_monitoring

Avoid using mutex in reset_vbat_monitoring() as this function is
already called holding the same mutex.

Change-Id: I18f361d78ee3a53f69e57265faa513987961f32b
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>