usb: dwc3: fix build warnings

usb: dwc3: fix build warnings

fix the following build warnings:

drivers/usb/dwc3/core.c: In function ‘dwc3_uboot_init’:
drivers/usb/dwc3/core.c:625:6: warning: ‘dev’ is used uninitialized in this function [-Wuninitialized]
mem = devm_kzalloc(dev, sizeof(*dwc) + DWC3_ALIGN_MASK, GFP_KERNEL);
        ^
drivers/usb/dwc3/dwc3-omap.c: In function ‘dwc3_omap_uboot_init’:
drivers/usb/dwc3/dwc3-omap.c:380:7: warning: ‘dev’ is used uninitialized in this function [-Wuninitialized]
omap = devm_kzalloc(dev, sizeof(*omap), GFP_KERNEL);

Signed-off-by: Felipe Balbi <balbi@ti.com>