drm/i915: Fix Sink CRC

In some cases like when PSR just got enabled the panel need more vblank
times to calculate CRC. I figured that out with the new PSR test cases
facing some cases that I had a green screen but a blank CRC. Even with
2 vblank waits on kernel + 2 vblank waits on test case.

So let's give up to 6 vblank wait time. However we now check for
TEST_CRC_COUNT that shows when panel finished to calculate CRC and
has it ready.

v2: Jani pointed out attempts decrements was wrong and should never reach
the error condition. And Daniel pointed out that EIO is more appropriated than
EGAIN. Also I realized that I have to read test_crc_count after setting
test_sink

v3: Rebase and adding error message

Cc: Todd Previte <tprevite@gmail.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Todd Previte <tprevite@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 9305c71..8edeed0 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -303,7 +303,8 @@
 #define DP_TEST_CRC_B_CB		    0x244
 
 #define DP_TEST_SINK_MISC		    0x246
-#define DP_TEST_CRC_SUPPORTED		    (1 << 5)
+# define DP_TEST_CRC_SUPPORTED		    (1 << 5)
+# define DP_TEST_COUNT_MASK		    0x7
 
 #define DP_TEST_RESPONSE		    0x260
 # define DP_TEST_ACK			    (1 << 0)
@@ -313,7 +314,7 @@
 #define DP_TEST_EDID_CHECKSUM		    0x261
 
 #define DP_TEST_SINK			    0x270
-#define DP_TEST_SINK_START	    (1 << 0)
+# define DP_TEST_SINK_START		    (1 << 0)
 
 #define DP_PAYLOAD_TABLE_UPDATE_STATUS      0x2c0   /* 1.2 MST */
 # define DP_PAYLOAD_TABLE_UPDATED           (1 << 0)