block: remove unused BLK_QC_T_EAGAIN flag

commit 7b6620d7db56 ("block: remove REQ_NOWAIT_INLINE") removed the
REQ_NOWAIT_INLINE related code, but the diff wasn't applied to
blk_types.h somehow.

Then commit 2771cefeac49 ("block: remove the REQ_NOWAIT_INLINE flag")
removed the REQ_NOWAIT_INLINE flag while the BLK_QC_T_EAGAIN flag still
remains.

Fixes: 7b6620d7db56 ("block: remove REQ_NOWAIT_INLINE")
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 4ecf4fe..b3fc5d3 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -497,13 +497,12 @@
 
 typedef unsigned int blk_qc_t;
 #define BLK_QC_T_NONE		-1U
-#define BLK_QC_T_EAGAIN		-2U
 #define BLK_QC_T_SHIFT		16
 #define BLK_QC_T_INTERNAL	(1U << 31)
 
 static inline bool blk_qc_t_valid(blk_qc_t cookie)
 {
-	return cookie != BLK_QC_T_NONE && cookie != BLK_QC_T_EAGAIN;
+	return cookie != BLK_QC_T_NONE;
 }
 
 static inline unsigned int blk_qc_t_to_queue_num(blk_qc_t cookie)