drm/i915/icl: Don't allocate fixed bypass path blocks for ICL

drm/i915/icl: Don't allocate fixed bypass path blocks for ICL

GEN9 onwards bypass path allocation of 4 blocks was needed, as per
hardware design. ICL doesn't require bypass path allocation of 4 DDB
blocks, handling the same in this patch.

v2 (from Paulo):
  - No need for a comment that says what the code already says.

Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: James Ausmus <james.ausmus@intel.com>
Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180130134918.32283-2-paulo.r.zanoni@intel.com