Rename option USBVERBOSE to USB_VERBOSE for 2 reasons:

1. USB_VERBOSE is more consistent with USB_DEBUG,
2. sys/dev/usb/usb_device.c uses option USB_VERBOSE and not USBVERBOSE.

POLA with the USBVERBOSE option as it's found in 7-STABLE
has been considered but found insignificant in the face
of the USB stack overhaul.

Approved by: re (kensmith)