[smbios] Expose board serial number as ${board-serial}

With blade servers, the chassis serial number (exposed via ${serial})
may not be unique.  Expose ${board-serial} as a named setting to
provide easy access to a more meaningful serial number.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/smbios.h

@@ -116,6 +116,23 @@ struct smbios_system_information {
 /** SMBIOS system information structure type */
 #define SMBIOS_TYPE_SYSTEM_INFORMATION 1
 
+/** SMBIOS base board information structure */
+struct smbios_base_board_information {
+	/** SMBIOS structure header */
+	struct smbios_header header;
+	/** Manufacturer string */
+	uint8_t manufacturer;
+	/** Product string */
+	uint8_t product;
+	/** Version string */
+	uint8_t version;
+	/** Serial number string */
+	uint8_t serial;
+} __attribute__ (( packed ));
+
+/** SMBIOS base board information structure type */
+#define SMBIOS_TYPE_BASE_BOARD_INFORMATION 2
+
 /** SMBIOS enclosure information structure */
 struct smbios_enclosure_information {
 	/** SMBIOS structure header */