power: pm8921-charger: Fix delay in USB wall-charger removal

Avoid scheduling time optimization for the vin_min work. This
prevents delay in USB removal detection for USB wall-charger.

CRs-Fixed: 579548
Change-Id: I578a0a70122e4d10ff932a41d6c6ac58e5ef121d
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>
Signed-off-by: Saket Saurabh <ssaurabh@codeaurora.org>