drm/i915: fix DP AUX register definitions on Haswell

The old rule that the AUX registers are just an offset (+4 and +10)
from output_reg is not true anymore, since output_reg in on the CPU
and some AUX regs are on the PCH.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
[danvet: use the existing #defines as spotted by Damien Lespiau.]
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dp.c

@@ -356,6 +356,29 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
 	uint32_t aux_clock_divider;
 	int try, precharge;
 
+	if (IS_HASWELL(dev)) {
+		switch (intel_dp->port) {
+		case PORT_A:
+			ch_ctl = DPA_AUX_CH_CTL;
+			ch_data = DPA_AUX_CH_DATA1;
+			break;
+		case PORT_B:
+			ch_ctl = PCH_DPB_AUX_CH_CTL;
+			ch_data = PCH_DPB_AUX_CH_DATA1;
+			break;
+		case PORT_C:
+			ch_ctl = PCH_DPC_AUX_CH_CTL;
+			ch_data = PCH_DPC_AUX_CH_DATA1;
+			break;
+		case PORT_D:
+			ch_ctl = PCH_DPD_AUX_CH_CTL;
+			ch_data = PCH_DPD_AUX_CH_DATA1;
+			break;
+		default:
+			BUG();
+		}
+	}
+
 	intel_dp_check_edp(intel_dp);
 	/* The clock divider is based off the hrawclk,
 	 * and would like to run at 2MHz. So, take the