smbios: Set BIOS release version

We may as well include the U-Boot release information in the type-0 table
since it is designed for that purpose.

U-Boot uses release versions based on the year and month. The year cannot
fit in a byte, so drop the century.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>