Record mediaprovider_tmpfs type for compatibility.

Commit: 3eed3eac added the compatibility
statement for the new mediaprovider app domain, but it missed another
new, private type, mediaprovider_tmpfs, that is automatically created for
all appdomains.  It replaces priv_app_tmpfs, but since both types are
private, they do not need to be added to the actual mapping (vendor policy
cannot use it).

Bug: 62573845
Test: None.  Prebuilt-only change.
Change-Id: I62229a5be74cd928fe0ca82a45b73cb61d6f5223

prebuilts/api/26.0/26.0.ignore.cil

@@ -11,6 +11,7 @@
     hal_tetheroffload_hwservice
     hal_wifi_offload_hwservice
     kmsg_debug_device
+    mediaprovider_tmpfs
     netd_stable_secret_prop
     sysfs_fs_ext4_features
     timezone_service