USB: core: Free the allocated memory before exiting on error

'new_interfaces' should be freed to avoid memory leak.

Cc: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>