tcgbios: Change format of S_CRTM_VERSION string to ucs-2

Change the format of the S_CRTM_VERSION string to ucs-2 since this
is what seems to be commonly used by other firmwares following
insight from a TCG work group member.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Tested-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>