smbios: Fallback to the default DT if sysinfo nodes are missing

smbios: Fallback to the default DT if sysinfo nodes are missing

In order to fill in the SMBIOS tables U-Boot currently relies on a
"u-boot,sysinfo-smbios" compatible node.  This is fine for the boards
that already include such nodes.  However with some recent EFI changes,
the majority of boards can boot up distros, which usually rely on
things like dmidecode etc for their reporting.  For boards that
lack this special node the SMBIOS output looks like:

System Information
        Manufacturer: Unknown
        Product Name: Unknown
        Version: Unknown
        Serial Number: Unknown
        UUID: Not Settable
        Wake-up Type: Reserved
        SKU Number: Unknown
        Family: Unknown

This looks problematic since most of the info are "Unknown".  The DT spec
specifies standard properties containing relevant information like
'model' and 'compatible' for which the suggested format is
<manufacturer,model>. Unfortunately the 'model' string found in DTs is
usually lacking the manufacturer so we can't use it for both
'Manufacturer' and 'Product Name' SMBIOS entries reliably.

So let's add a last resort to our current smbios parsing.  If none of
the sysinfo properties are found, scan for those information in the
root node of the device tree. Use the 'model' to fill the 'Product
Name' and the first value of 'compatible' for the 'Manufacturer', since
that always contains one.

pre-patch:
Handle 0x0001, DMI type 1, 27 bytes
System Information
        Manufacturer: Unknown
        Product Name: Unknown
        Version: Unknown
        Serial Number: 100000000bb24ceb
        UUID: 30303031-3030-3030-3061-613234636435
        Wake-up Type: Reserved
        SKU Number: Unknown
        Family: Unknown
[...]

and post patch:
Handle 0x0001, DMI type 1, 27 bytes
System Information
        Manufacturer: raspberrypi
        Product Name: Raspberry Pi 4 Model B Rev 1.1
        Version: Unknown
        Serial Number: 100000000bb24ceb
        UUID: 30303031-3030-3030-3061-613234636435
        Wake-up Type: Reserved
        SKU Number: Unknown
        Family: Unknown
[...]

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Peter Robinson <pbrobinson@gmail.com>
Tested-by: Peter Robinson <pbrobinson@gmail.com>