power: smb135x-charger: fix charging disable use-case

In case of BMS controlled charging the charging gets disabled
at 100% SOC by enabling USB suspend mode.
SMB135x charger has two separate paths for power output viz. charging
and system-supply.
USB suspend mode disables both charging and system-supply path and
thus prevents charger to supply to system.
Fix this by explicitly disabling charging instead of USB suspend at
100% SOC.

CRs-Fixed: 768546
Change-Id: I41188d69c864f920faae7a4758ff5263cc0522fd
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>