anv: store heap address bounds when initializing physical device

anv: store heap address bounds when initializing physical device

We can then reuse those bounds to initialize the VMA heaps at logical
device creation.

This fixes an issue on EHL which has only 36bits of VMA. We were
incorrectly using the fixed 48bits upper bound to initialize the
logical device heap, resulting in addresses beyong the device's
limits.

v2: Don't confuse heap size (limited by system memory) and VMA size
   (limited by number of addressing bits the platform has)

v3: Fix low heap vma_size :( (Lionel)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reported-by: James Xiong <james.xiong@intel.com>
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com> (v1)
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net> (v2)