usb: xhci-msm-hsic: Fix vddmin voting for vddcx regulator

Driver is incorrectly setting RPM_REGULATOR_CORNER_NORMAL as
minimum required voltage for vddcx regulator to vote for vddmin.
Fix this by setting RPM_REGULATOR_CORNER_NONE as minimum required
voltage when voting for vddmin.

Change-Id: I1af39e8c283f9a57f300439e388177c9dcf0c56a
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>