anv: Stop tracking VMA allocations

util_vma_heap_alloc will already return 0 if it doesn't have enough
space.  The only thing the vma_*_available tracking was doing was
preventing us from allocating too much on any given heap.  Now that
we're tracking that in the heap itself, we can drop these.

Reviewed-by: Ivan Briano <ivan.briano@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>

src/intel/vulkan/anv_private.h

@@ -1214,8 +1214,6 @@ struct anv_device {
     pthread_mutex_t                             vma_mutex;
     struct util_vma_heap                        vma_lo;
     struct util_vma_heap                        vma_hi;
-    uint64_t                                    vma_lo_available;
-    uint64_t                                    vma_hi_available;
 
     /** List of all anv_device_memory objects */
     struct list_head                            memory_objects;