xprtrdma: Clean up unused RPCRDMA_INLINE_PAD_THRESH macro

Fixes: b3221d6a53c4 ('xprtrdma: Remove logic that constructs...')
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

include/linux/sunrpc/xprtrdma.h

@@ -54,8 +54,6 @@
 
 #define RPCRDMA_DEF_INLINE  (1024)	/* default inline max */
 
-#define RPCRDMA_INLINE_PAD_THRESH  (512)/* payload threshold to pad (bytes) */
-
 /* Memory registration strategies, by number.
  * This is part of a kernel / user space API. Do not remove. */
 enum rpcrdma_memreg {