btrfs: fix trace event name typo for FLUSH_DELAYED_REFS

Fix a typo of printing FLUSH_DELAYED_REFS event in flush_space() as
FLUSH_ELAYED_REFS.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

include/trace/events/btrfs.h

@@ -98,7 +98,7 @@ struct raid56_bio_trace_info;
 	EM( FLUSH_DELALLOC_WAIT,	"FLUSH_DELALLOC_WAIT")		\
 	EM( FLUSH_DELALLOC_FULL,	"FLUSH_DELALLOC_FULL")		\
 	EM( FLUSH_DELAYED_REFS_NR,	"FLUSH_DELAYED_REFS_NR")	\
-	EM( FLUSH_DELAYED_REFS,		"FLUSH_ELAYED_REFS")		\
+	EM( FLUSH_DELAYED_REFS,		"FLUSH_DELAYED_REFS")		\
 	EM( ALLOC_CHUNK,		"ALLOC_CHUNK")			\
 	EM( ALLOC_CHUNK_FORCE,		"ALLOC_CHUNK_FORCE")		\
 	EM( RUN_DELAYED_IPUTS,		"RUN_DELAYED_IPUTS")		\