drm/i915/psr/cnl: Set y-coordinate as valid in SDP

This was my bad, spec says that the name of this bit is
'Y-coordinate valid' but the values for it is:
0: Include Y-coordinate valid eDP1.4a
1: Do not include Y-coordinate valid eDP 1.4
So not setting it.

BSpec: 7713

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180425212334.21109-4-jose.souza@intel.com