efi_loader: Introduce eventlog support for TCG2_PROTOCOL

In the previous patches we only introduced a minimal subset of the
EFI_TCG2_PROTOCOL protocol implementing GetCapability().
So let's continue adding features to it, introducing the
GetEventLog() and HashLogExtendEvent() functions.

In order to do that we first need to construct the eventlog in memory,
specifically in EFI_BOOT_SERVICES_DATA memory and a configuration table
from EFI_ACPI_MEMORY_NVS.
U-Boot won't currently add any events to the log or measure any
components, but will expose the necessary EFI APIs for applications
to do so.

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>