[PATCH] drm/i915/gt: Limit the reserved VM space to only the platforms that need it

[Mrozek, Michal]

Commit 9bb66c179f50 ("drm/i915: Reserve some kernel space per
vm") reduces the available VM space of one page in order to apply
Wa_16018031267 and Wa_16018063123.

This page was reserved indiscrimitely in all platforms even when not needed. Limit it to DG2 onwards.

Fixes: 9bb66c179f50 ("drm/i915: Reserve some kernel space per vm")
Signed-off-by: Andi Shyti <andi.shyti at linux.intel.com>
Cc: Andrzej Hajda <andrzej.hajda at intel.com>
Cc: Chris Wilson <chris.p.wilson at linux.intel.com>
Cc: Jonathan Cavitt <jonathan.cavitt at intel.com>
Cc: Nirmoy Das <nirmoy.das at intel.com>

Acked-by: Michal Mrozek <michal.mrozek at intel.com>