Disable GPU hang by default on unrecoverable ECC cache errors.

v2:
 * Rebase.

v3:
 * Use intel_uncore_read. (Chris)

Fixes: cc38cae7 ("drm/i915/icl: Introduce initial Icelake Workarounds")
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190520110442.403-2-tvrtko.ursulin@linux.intel.com