msm: kgsl: Enable 64 bit map if everybody is willing

All the pieces have now come into place to allow for 64 bit mappings.
The only thing left to do is to enable it so make it so.

Change-Id: Ic0dedbad3615a4e8dbef53f64adae6e28b610251
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>