masking return value of usb_control_msg() will mask negative
error values into positive.
Cc: Mike Thomas <rmthomas@sciolus.org> Reported-by: Dan Carpenter <error27@gmail.com> Signed-off-by: Tomas Winkler <tomas.winkler@intel.com> Reviewed-by: Dan Carpenter <error27@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>