usb: dwc3_otg: Remove logic to manually set BSV

Removes logic to manually override BSV. Instead rely
on psy framework to set BSV. This is also applicable
to emulation platform scenarios.

Change-Id: I96a1a14edfe4462657835b1512de13014f36c734
Signed-off-by: Devdutt Patnaik <dpatnaik@codeaurora.org>
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>