drm/i915/cnl: Fix wrpll math for higher freqs.

Spec describe all values in MHz. We handle our
clocks in KHz. This includes the best_dco_centrality that was
forgot in the same unity as spec. Consequently we couldn't
get a good divider for high frequenies. Hence HDMI 2.0 wasn't
working.

Spec tells 999999 for initial best_dco_centrality meaning the
max value in MHz.
Since we convert dco from MHz to KHz we also need to convert
this initial best_doc_centrality to 999999000 or 999999999
or even better, to the max that its variable allow.

This patch also replaces the use of "* KHz(1)" with the values
directly on KHz to avoid future confusion.

v2: Use U32_MAX instead of random 99999 as spec tells. (Ville).

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Shashank Sharma <shashank.sharma@intel.com>
Cc: Mika Kahola <mika.kahola@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: James Ausmus <james.ausmus@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171114234223.10600-1-rodrigo.vivi@intel.com

drivers/gpu/drm/i915/intel_dpll_mgr.c

@@ -2201,8 +2201,8 @@ cnl_ddi_calculate_wrpll(int clock,
 			struct skl_wrpll_params *wrpll_params)
 {
 	u32 afe_clock = clock * 5;
-	u32 dco_min = 7998 * KHz(1);
-	u32 dco_max = 10000 * KHz(1);
+	u32 dco_min = 7998000;
+	u32 dco_max = 10000000;
 	u32 dco_mid = (dco_min + dco_max) / 2;
 	static const int dividers[] = {  2,  4,  6,  8, 10, 12,  14,  16,
 					 18, 20, 24, 28, 30, 32,  36,  40,
@@ -2211,7 +2211,7 @@ cnl_ddi_calculate_wrpll(int clock,
 					 84, 88, 90, 92, 96, 98, 100, 102,
 					  3,  5,  7,  9, 15, 21 };
 	u32 dco, best_dco = 0, dco_centrality = 0;
-	u32 best_dco_centrality = 999999;
+	u32 best_dco_centrality = U32_MAX; /* Spec meaning of 999999 MHz */
 	int d, best_div = 0, pdiv = 0, qdiv = 0, kdiv = 0;
 
 	for (d = 0; d < ARRAY_SIZE(dividers); d++) {