drm/i915/tgl: Add DC3CO required register and bits

Adding following definition to i915_reg.h
1. DC_STATE_EN register DC3CO bit fields and masks.
   DC3CO enable bit will be used by driver to make DC3CO
   ready for DMC f/w and status bit will be used as DC3CO
   entry status.
2. Transcoder EXITLINE register and its bit fields and mask.
   Transcoder EXITLINE enable bit represents PSR2 idle frame
   reset should be applied at exit line and exitlines mask
   represent required number of scanlines at which DC3CO
   exit happens.

   B.Specs:49196

v1: Use of REG_BIT and using extra space for EXITLINE_ macro
    definition. [Animesh]
v2: Grouping EXITLINE reg bits with EXITLINE(trans) define,
    no functional change. [Ville]

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Animesh Manna <animesh.manna@intel.com>
Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191007094607.2111-1-anshuman.gupta@intel.com

drivers/gpu/drm/i915/i915_reg.h

@@ -4145,6 +4145,7 @@ enum {
 #define _VTOTAL_A	0x6000c
 #define _VBLANK_A	0x60010
 #define _VSYNC_A	0x60014
+#define _EXITLINE_A	0x60018
 #define _PIPEASRC	0x6001c
 #define _BCLRPAT_A	0x60020
 #define _VSYNCSHIFT_A	0x60028
@@ -4196,6 +4197,11 @@ enum {
 #define PIPESRC(trans)		_MMIO_TRANS2(trans, _PIPEASRC)
 #define PIPE_MULT(trans)	_MMIO_TRANS2(trans, _PIPE_MULT_A)
 
+#define EXITLINE(trans)		_MMIO_TRANS2(trans, _EXITLINE_A)
+#define   EXITLINE_ENABLE	REG_BIT(31)
+#define   EXITLINE_MASK		REG_GENMASK(12, 0)
+#define   EXITLINE_SHIFT	0
+
 /*
  * HSW+ eDP PSR registers
  *
@@ -10291,6 +10297,8 @@ enum skl_power_gate {
 /* GEN9 DC */
 #define DC_STATE_EN			_MMIO(0x45504)
 #define  DC_STATE_DISABLE		0
+#define  DC_STATE_EN_DC3CO		REG_BIT(30)
+#define  DC_STATE_DC3CO_STATUS		REG_BIT(29)
 #define  DC_STATE_EN_UPTO_DC5		(1 << 0)
 #define  DC_STATE_EN_DC9		(1 << 3)
 #define  DC_STATE_EN_UPTO_DC6		(2 << 0)