drm/i915: Name the "iboost bit"

Give a proper name for the SKL DDI_BUF_TRANS iboost bit.

Cc: David Weinehall <david.weinehall@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1468328376-6380-3-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: David Weinehall <david.weinehall@linux.intel.com>

drivers/gpu/drm/i915/i915_reg.h

@@ -7487,6 +7487,7 @@ enum {
 #define _DDI_BUF_TRANS_A		0x64E00
 #define _DDI_BUF_TRANS_B		0x64E60
 #define DDI_BUF_TRANS_LO(port, i)	_MMIO(_PORT(port, _DDI_BUF_TRANS_A, _DDI_BUF_TRANS_B) + (i) * 8)
+#define  DDI_BUF_BALANCE_LEG_ENABLE	(1 << 31)
 #define DDI_BUF_TRANS_HI(port, i)	_MMIO(_PORT(port, _DDI_BUF_TRANS_A, _DDI_BUF_TRANS_B) + (i) * 8 + 4)
 
 /* Sideband Interface (SBI) is programmed indirectly, via

drivers/gpu/drm/i915/intel_ddi.c

@@ -434,7 +434,7 @@ void intel_prepare_ddi_buffer(struct intel_encoder *encoder)
 		/* If we're boosting the current, set bit 31 of trans1 */
 		if (dev_priv->vbt.ddi_port_info[port].hdmi_boost_level ||
 		    dev_priv->vbt.ddi_port_info[port].dp_boost_level)
-			iboost_bit = 1<<31;
+			iboost_bit = DDI_BUF_BALANCE_LEG_ENABLE;
 
 		if (WARN_ON(encoder->type == INTEL_OUTPUT_EDP &&
 			    port != PORT_A && port != PORT_E &&