VFS: Fix up some ->d_inode accesses in the chelsio driver

Fix up some ->d_inode accesses in the chelsio driver.

 (1) FILE_DATA() should just be replaced with file_inode().

 (2) set_debugfs_file_size() should be removed and debugfs_create_file_size()
     should be used to create the file.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>