drm/i915/tgl: Fix the Wa number of a fix

The Wa number for this fix is Wa_1607087056 the BSpec bug id is
1607087056, just updating to match BSpec.

BSpec: 52890
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200227220101.321671-7-jose.souza@intel.com