test: Add more SMBIOS data to sandbox

Some common smbios settings are not included with sandbox. Add these to
test.dts so the data is more meaningful.

Update smbios tests to match the new devicetree values.

Co-developed-by: Claude <noreply@anthropic.com>
Signed-off-by: Simon Glass <sjg@chromium.org>

test/py/tests/test_smbios.py

@@ -34,7 +34,7 @@ def test_cmd_smbios_sandbox(ubman):
     assert 'DMI type 0,' in output
     assert 'Vendor: U-Boot' in output
     assert 'DMI type 1,' in output
-    assert 'Manufacturer: sandbox' in output
+    assert 'Manufacturer: Sandbox Corp' in output
     assert 'DMI type 2,' in output
     assert 'DMI type 3,' in output
     assert 'DMI type 4,' in output