drm/i915/skl: Read the Memory Latency Values for WM computation

This patch reads the memory latency values for all the 8 levels for
SKL. These values are needed for the Watermark computation.

v2: Incorporated the review comments from Damien on register
    indentation.

v3: Updated the code to use the sandybridge_pcode_read for reading
    memory latencies for GEN9.

v4: Don't put gen 9 in the middle of an ordered list of ifs
    (Damien)

v5: take the rps.hw_lock around sandybridge_pcode_read() (Damien)

v6: Use gen >= 9 in the pcode_read() function for data1.
    Move the defines near the gen6 ones and prefix them with PCODE.
    Remove unused timeout define (the pcode_read() code has a larger
    timeout already).

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Pradeep Bhat <pradeep.bhat@intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 54691bc..05fcbe5 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1678,6 +1678,12 @@
 		uint16_t spr_latency[5];
 		/* cursor */
 		uint16_t cur_latency[5];
+		/*
+		 * Raw watermark memory latency values
+		 * for SKL for all 8 levels
+		 * in 1us units.
+		 */
+		uint16_t skl_latency[8];
 
 		/* current hardware state */
 		struct ilk_wm_values hw;