EHCI: HSIC: Perform msm_bus voting update in workqueue context

It is observed that sometimes msm_bus voting upate API taking
longer time to return which delays the HSIC resume sequence
which is time critical.

CRs-Fixed: 388430
Change-Id: I5ad93ee4bbea2b83dad8cc5c8ece8b72ee433d9f
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>