Switch XENCRSH to grant v1

Signed-off-by: Owen Smith <owen.smith@citrix.com>
Fix comments on prev commit
* #define MAXIMUM_GRANT_PAGES 1
* KeMemoryBarrier()

Signed-off-by: Owen Smith <owen.smith@citrix.com>
Merge pull request #7 from OwenSmith/switch-xencrsh-to-grant-v1

Switch xencrsh to grant v1