blkparse: fix allowed event type specifiers for custom output format

'W' was replaced by 'B' in code but 'W' was not removed from valid specs.

'W' (and 'X' for split) had been added to valid specs as a side effect of remap action support ('A') in commit a8f30e64d4d3 ("[PATCH] Add support for remap actions").

---
 blkparse_fmt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index c42e6d7b7219..c110dad10b0b 100644
@@ -11,7 +11,7 @@
 
 #include "blktrace.h"
 
-#define VALID_SPECS	"ABCDFGIMPQRSTUWX"
+#define VALID_SPECS	"ABCDFGIMPQRSTUX"
 
 #define HEADER		"%D %2c %8s %5T.%9t %5p %2a %3d "
 

2.14.2