shim: trigger to record further logs to tcg 2.0 final event log area

shim: trigger to record further logs to tcg 2.0 final event log area

According to TCG EFI Protocol Specification for TPM 2.0 family,
all events generated after the invocation of EFI_TCG2_GET_EVENT_LOG
shall be stored in an instance of an EFI_CONFIGURATION_TABLE aka
EFI TCG 2.0 final events table. Hence, it is necessary to trigger the
internal switch through calling get_event_log() in order to allow
to retrieve the logs from OS runtime.

Signed-off-by: Lans Zhang <jia.zhang@windriver.com>