SMBIOS: Build aggregate smbios tables and entry point

Build an aggregate set of smbios tables and an entry point structure.

Insert tables and entry point into fw_cfg respectively under
"etc/smbios/smbios-tables" and "etc/smbios/smbios-anchor".

Machine types <= 2.0 will for now continue using field-by-field
overrides to SeaBIOS defaults, but for machine types 2.1 and up we
expect the BIOS to look for and use the aggregate tables generated
by this patch.

Signed-off-by: Gabriel Somlo <somlo@cmu.edu>

[ kraxel: fix 32bit build ]

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>