rpmsg: virtio: Free driver_override when rpmsg_remove()

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

rpmsg: virtio: Free driver_override when rpmsg_remove()

Free driver_override when rpmsg_remove(), otherwise

the following memory leak will occur:

unreferenced object 0xffff0000d55d7080 (size 128):

comm "kworker/u8:2", pid 56, jiffies 4294893188 (age 214.272s)

hex dump (first 32 bytes):

72 70 6d 73 67 5f 6e 73 00 00 00 00 00 00 00 00 rpmsg_ns........

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................

backtrace:

[<000000009c94c9c1>] __kmem_cache_alloc_node+0x1f8/0x320

[<000000002300d89b>] __kmalloc_node_track_caller+0x44/0x70

[<00000000228a60c3>] kstrndup+0x4c/0x90

[<0000000077158695>] driver_set_override+0xd0/0x164

[<000000003e9c4ea5>] rpmsg_register_device_override+0x98/0x170

[<000000001c0c89a8>] rpmsg_ns_register_device+0x24/0x30

[<000000008bbf8fa2>] rpmsg_probe+0x2e0/0x3ec

[<00000000e65a68df>] virtio_dev_probe+0x1c0/0x280

[<00000000443331cc>] really_probe+0xbc/0x2dc

[<00000000391064b1>] __driver_probe_device+0x78/0xe0

[<00000000a41c9a5b>] driver_probe_device+0xd8/0x160

[<000000009c3bd5df>] __device_attach_driver+0xb8/0x140

[<0000000043cd7614>] bus_for_each_drv+0x7c/0xd4

[<000000003b929a36>] __device_attach+0x9c/0x19c

[<00000000a94e0ba8>] device_initial_probe+0x14/0x20

[<000000003c999637>] bus_probe_device+0xa0/0xac