vfio: Fix memory leak of hostwin

vfio: Fix memory leak of hostwin

hostwin is allocated and added to hostwin_list in vfio_host_win_add, but
it is only deleted from hostwin_list in vfio_host_win_del, which causes
a memory leak.  Also, freeing all elements in hostwin_list is missing in
vfio_disconnect_container.

Fix: 2e4109de8e58 ("vfio/spapr: Create DMA window dynamically (SPAPR IOMMU v2)")
CC: qemu-stable@nongnu.org
Signed-off-by: Peng Liang <liangpeng10@huawei.com>
Link: https://lore.kernel.org/r/20211117014739.1839263-1-liangpeng10@huawei.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>