USB: mos7840.c: remove dbg() tracing calls

dbg() was used a lot a long time ago to trace code flow.  Now that we have
ftrace, this isn't needed at all, so remove these calls.

CC: Johan Hovold <jhovold@gmail.com>
CC: Donald Lee <donald@asix.com.tw>
CC: Rusty Russell <rusty@rustcorp.com.au>
CC: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>