dwc3: core: Update dwc->reg_phys information

USB GSI endpoint related register offset is passed from dwc3-msm
driver. Without dwc->reg_phys address updated, wrong offset is
passed for DEPCMD register which results into IPA firmware
getting bus errors. Fix this issue by updating dwc->reg_phys.

Change-Id: I0b69fa5cd8432b8a3978449ef5659dcd69774bde
Signed-off-by: Mayank Rana <mrana@codeaurora.org>