drm/i915: Remove references to previously removed UMS config option

drm/i915: Remove references to previously removed UMS config option

Commit 03dae59c72ffffd8 ("drm/i915: Ditch UMS config option") removed
CONFIG_DRM_I915_UMS from the Kconfig file, but i915_drv.c still
references this option in two #ifndef statements.

As an undefined config option will always be 'false', we can drop
the #ifndefs alltogether and adapt the printed error message.

This inconsistency was found with the undertaker tool.

Signed-off-by: Andreas Ruprecht <rupran@einserver.de>
[danvet: Undo logging change as requested by Jani.]
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>