orangefs: remove redundant assignment to variable buffer_index

The variable buffer_index is assigned a value that is never read,
it is assigned just before the function returns. The assignment is
redundant and can be removed.

Cleans up clang scan build warning:
fs/orangefs/file.c:276:3: warning: Value stored to 'buffer_index'
is never read [deadcode.DeadStores]
Signed-off-by: NColin Ian King <colin.i.king@gmail.com>
Signed-off-by: NMike Marshall <hubcap@omnibond.com>

fs/orangefs/file.c

@@ -273,7 +273,6 @@ ssize_t wait_for_direct_io(enum ORANGEFS_io_type type, struct inode *inode,
 		gossip_debug(GOSSIP_FILE_DEBUG,
 			"%s(%pU): PUT buffer_index %d\n",
 			__func__, handle, buffer_index);
-		buffer_index = -1;
 	}
 	op_release(new_op);
 	return ret;