anv: Stop tracking VMA allocations

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>