intel: add dependency on genxml generated files

intel: add dependency on genxml generated files

Drivers using genxml will start compilation before generated files are
created, so add a dependency to it.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
Cc: mesa-stable@lists.freedesktop.org