drm/i915: extend lpt_enable_clkout_dp

Now it implements 3 different sequences from BSpec and also has
support for ULT.

v2: - Change IS_ULT checks for LPT-LP checks
    - Add check for LPT-LP + with_fdi (Ben)
    - Merge DBUFF0/GEN0 bit definitions since they're the same
      register (Ben)
    - DBUFF0 (1<<0) is Disable, not Enable

Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index e20f093..0dfcbad 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -4942,7 +4942,8 @@
 #define  SBI_SSCAUXDIV6				0x0610
 #define   SBI_SSCAUXDIV_FINALDIV2SEL(x)		((x)<<4)
 #define  SBI_DBUFF0				0x2a00
-#define   SBI_DBUFF0_ENABLE			(1<<0)
+#define  SBI_GEN0				0x1f00
+#define   SBI_GEN0_CFG_BUFFENABLE_DISABLE	(1<<0)
 
 /* LPT PIXCLK_GATE */
 #define PIXCLK_GATE			0xC6020