smb: client: short-circuit in open_cached_dir_by_dentry() if !dentry
When dentry is NULL, the current code acquires the spinlock and traverses
the entire list, but the condition (dentry && cfid->dentry == dentry)
ensures no match will ever be found.
Return -ENOENT early in this case, avoiding unnecessary lock acquisition
and list traversal.
Signed-off-by: Henrique Carvalho <henrique.carvalho@suse.com> Signed-off-by: Steve French <stfrench@microsoft.com>