usb: dwc3: gadget: Fix sparse warnings

This patch fixes the following sparse warnings:

drivers/usb/dwc3/gadget.c:1096:7: warning: symbol 'ret' shadows an earlier one
drivers/usb/dwc3/gadget.c:1058:8: originally declared here
drivers/usb/dwc3/gadget.c:1100:16: warning: symbol 'dwc' shadows an earlier one
drivers/usb/dwc3/gadget.c:1057:15: originally declared here
drivers/usb/dwc3/gadget.c:1118:16: warning: symbol 'dwc' shadows an earlier one
drivers/usb/dwc3/gadget.c:1057:15: originally declared here
drivers/usb/dwc3/gadget.c:1800:19: warning: symbol 'dep' shadows an earlier one
drivers/usb/dwc3/gadget.c:1778:18: originally declared here

Also, fix the potential checkpatch errors around the if() loops that
this fix patch can create.

Signed-off-by: Moiz Sonasath <m-sonasath@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>