autofs4: Wrong format for printing dentry

%pD for struct file*, %pd for struct dentry*.

Fixes: a455589f

 ("assorted conversions to %p[dD]")
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>