drm/i915/tgl: Add Wa number to WaAllowPMDepthAndInvocationCountAccessFromUMD

Just to make easier to check that the Wa was implemetend when
comparing to the number in BSpec.

BSpec: 52890
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200227220101.321671-10-jose.souza@intel.com