vdpa/vp_vdpa: fix kfree a wrong pointer in vp_vdpa_remove

vdpa/vp_vdpa: fix kfree a wrong pointer in vp_vdpa_remove

In vp_vdpa_remove(), the code kfree(&vp_vdpa_mgtdev->mgtdev.id_table) uses
a reference of pointer as the argument of kfree, which is the wrong pointer
and then may hit crash like this:

Unable to handle kernel paging request at virtual address 00ffff003363e30c
Internal error: Oops: 96000004 [#1] SMP
Call trace:
 rb_next+0x20/0x5c
 ext4_readdir+0x494/0x5c4 [ext4]
 iterate_dir+0x168/0x1b4
 __se_sys_getdents64+0x68/0x170
 __arm64_sys_getdents64+0x24/0x30
 el0_svc_common.constprop.0+0x7c/0x1bc
 do_el0_svc+0x2c/0x94
 el0_svc+0x20/0x30
 el0_sync_handler+0xb0/0xb4
 el0_sync+0x160/0x180
Code: 54000220 f9400441 b4000161 aa0103e0 (f9400821)
SMP: stopping secondary CPUs
Starting crashdump kernel...

Fixes: ffbda8e9df10 ("vdpa/vp_vdpa : add vdpa tool support in vp_vdpa")
Signed-off-by: Rong Wang <wangrong68@huawei.com>
Signed-off-by: Nanyong Sun <sunnanyong@huawei.com>
Message-Id: <20221207120813.2837529-1-sunnanyong@huawei.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cindy Lu <lulu@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>