drm/i915: Revert "drm/i915/tgl: Wa_1607138340"

This reverts commit 08fff7ae.

For some yet unexplained reason not having this improves stability of some
media workloads.

Promise is that the media hang will be root caused properly and in the
meantime absence of this workaround is unlikely to cause problems.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Sudeep Dutt <sudeep.dutt@intel.com>
Cc: Francesco Balestrieri <francesco.balestrieri@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tony Ye <tony.ye@intel.com>
Acked-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200108161954.29739-1-tvrtko.ursulin@linux.intel.com