There's is another register (a read only, so no harm done) at 0x42020 on
Haswell GPUs. Let's just remove the write from the copy&paste that
introduced haswell_init_clock_gating().

A note for the interested reader, it does seem we have a duplication of
the 0x42020 register definition, hence the removal of 2 writes. That
duplication could be the object of a later patch.
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Tested-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>