USB: uss720.c: move assignment out of if () block

We should not be doing assignments within an if () block
so fix up the code to not do this.

change was created using Coccinelle.

CC: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Felipe Balbi <balbi@ti.com>