Most constants defined in xe_drm.h use DRM_XE_ as prefix which is
helpful to identify the name space. Make this systematic and add
this prefix where it was missing.

v2:
- fix vertical alignment of define values
- remove double DRM_ in some variables (José Roberto de Souza)

v3: Rebase
Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>