ANDROID: abi_gki_aarch64_whitelist: add module_layout and task_struct

The module_layout symbol is a special case that is always kept exported,
even with CONFIG_TRIM_UNUSED_KSYMS=y.

task_struct is special in a different way. It can be accessed without
the use of an exported symbol through direct register access.

Add them to the global whitelist to ensure they are kept stable.

Bug: 148277666
Bug: 147380000

Change-Id: Ib7ff326fd25da773e4dadc273ff60ec37b9f2bff
Signed-off-by: Matthias Maennich <maennich@google.com>