ANDROID: sdcardfs: fix itnull.cocci warnings

List_for_each_entry has the property that the first argument is always
bound to a real list element, never NULL, so testing dentry is not needed.

Generated by: scripts/coccinelle/iterators/itnull.cocci

Change-Id: I51033a2649eb39451862b35b6358fe5cfe25c5f5
Cc: Daniel Rosenberg <drosen@google.com>
Signed-off-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Guenter Roeck <groeck@chromium.org>