efi: libstub/tpm: enable tpm eventlog function for ARM platforms

Wire up the existing code for ARM that loads the TPM event log into
OS accessible buffers while running the EFI stub so that the kernel
proper can access it at runtime.

Tested-by: Zou Cao <zoucao@linux.alibaba.com>
Signed-off-by: Xinwei Kong <kong.kongxinwei@hisilicon.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>