drm/i915/cnl: Do not add an extra page for precaution in the Gen10 LRC size

BSpec indicates exactly 16752 DWORDs (17 pages), plus one page for PPHWSP. Please
notice that, when looking at the BSpec context image table, the right filter has
to be applied (e.g. "CNL") as some rows are excluded for specific GENs.

BSpec: 1383

v2: Update count and add BSpec tag (Joonas)
v3: Warning about filters in the commit message (Joonas)

Suggested-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Fixes: 7fd0b1a2 ("drm/i915/cnl: Add Gen10 LRC size")
Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1507131592-29209-1-git-send-email-oscar.mateo@intel.com


Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>