drm/xe: REBAR resize should be best effort

The resizing of the PCI BAR is a best effort feature.  If it is
not available, it should not fail the driver probe.

Rework the resize to not exit on failure.

Fixes: 7f075300

 ("drm/xe: Simplify rebar sizing")
Acked-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>