usb: musb: fix compile error

commit 35a83365da6aa10095c6138cc428c15853409c32
(usb: musb: drop unneeded musb_debug trickery)
introduced a compile error for blackfin and
tusb6010 glue layers. Fix it.

Reported-by: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>