USB: usbtest displays diagnostics again

Minor cleanup to the "usbtest" driver, mostly to resolve a regression:
all the important diagnostics were at KERN_DEBUG, so that when the
"#define DEBUG" was removed from the top of that file it stopped
providing diagnostics.  Fix by using KERN_ERROR.  Also:

 - Stop using the legacy dbg() calls
 - Simplify the internal debug macros
 - Correct some test descriptions:
	* Test #10 subcase 7 should *always* stall
	* Test #10 subcase 8 *may* stall
 - Diagnostic about control queue test failures is more informative
 - Fix some whitespace "bugs"

And add a warning about the rude interaction between usbfs ioctl()
and khubd during device disconnect ... don't unplug a device under
test, that will wedge.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>