anv: report HOST_ALLOCATION as supported for images

Report VK_EXTERNAL_MEMORY_HANDLE_TYPE_HOST_ALLOCATION_BIT_EXT as
supported for images. It was being shown supported for buffers, but not
images.

Fixes: 69cc6272 ("anv: Implement VK_EXT_external_memory_host")

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
(cherry picked from commit 832cedfd)