drm/i915: Silently fallback to 4k scratch

If we fail to allocate a 64k hugepage for scratch, we try again with a
normal 4k page (with some loss of efficiency at runtime). As we handle
this gracefully, we do not need a noisy allocation failure warning.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171010111005.13625-1-chris@chris-wilson.co.uk


Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>