vdpa_sim_blk: set number of address spaces and virtqueue groups

In the Linux kernel, the following vulnerability has been resolved: vdpa_sim_blk: set number of address spaces and virtqueue groups Commit bda324fd037a ("vdpasim: control virtqueue support") added two new fields (nas, ngroups) to vdpasim_dev_attr, but we forgot to initialize them for vdpa_sim_blk. When creating a new vdpa_sim_blk device this causes the kernel to panic in this way:    $ vdpa dev add mgmtdev vdpasim_blk name blk0    BUG: kernel NULL pointer dereference, address: 0000000000000030    ...    RIP: 0010:vhost_iotlb_add_range_ctx+0x41/0x220 [vhost_iotlb]    ...    Call Trace:     <TASK>     vhost_iotlb_add_range+0x11/0x800 [vhost_iotlb]     vdpasim_map_range+0x91/0xd0 [vdpa_sim]     vdpasim_alloc_coherent+0x56/0x90 [vdpa_sim]     ... This happens because vdpasim->iommu[0] is not initialized when dev_attr.nas is 0. Let's fix this issue by initializing both (nas, ngroups) to 1 for vdpa_sim_blk.