MIPS: vpe-mt: fix possible memory leak while module exiting

In the Linux kernel, the following vulnerability has been resolved:

MIPS: vpe-mt: fix possible memory leak while module exiting

Afer commit 1fa5ae857bb1 ("driver core: get rid of struct device's bus_id string array"), the name of device is allocated dynamically, it need be freed when module exiting, call put_device() to give up reference, so that it can be freed in kobject_cleanup() when the refcount hit to 0. The vpe_device is static, so remove kfree() from vpe_device_release().