usb: dwc3: Fix string format warnings

A number of strings were missing the format type due to a typo.

Fixes: 82dc6471 ("usb: dwc3: Keep track of interrupt statistics")
Change-Id: Ic0dedbad10b3641a21d9dce4a7d5d79116d20ba4
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>