Revert "drm/i915: W/A for underruns with WM1+ disabled on icl"

This reverts commit bf002c10.

The hw team has come up with a better workaround. So
let's get rid of this one.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190213165424.22904-1-ville.syrjala@linux.intel.com


Reviewed-by: Clint Taylor <Clinton.A.Taylor@intel.com>