drm/i915/reg: add stream splitter configuration definitions

The splitter configuration is required for eDP MSO.

Bspec: 50174
Cc: Nischal Varide <nischal.varide@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/443ad1fbf908800ee4e09315cb6a7ba26c64d136.1613054234.git.jani.nikula@intel.com

drivers/gpu/drm/i915/i915_reg.h

@@ -11447,6 +11447,9 @@ enum skl_power_gate {
 #define  BIG_JOINER_ENABLE			(1 << 29)
 #define  MASTER_BIG_JOINER_ENABLE		(1 << 28)
 #define  VGA_CENTERING_ENABLE			(1 << 27)
+#define  SPLITTER_CONFIGURATION_MASK		REG_GENMASK(26, 25)
+#define  SPLITTER_CONFIGURATION_2_SEGMENT	REG_FIELD_PREP(SPLITTER_CONFIGURATION_MASK, 0)
+#define  SPLITTER_CONFIGURATION_4_SEGMENT	REG_FIELD_PREP(SPLITTER_CONFIGURATION_MASK, 1)
 
 #define _ICL_PIPE_DSS_CTL2_PB			0x78204
 #define _ICL_PIPE_DSS_CTL2_PC			0x78404