[smbios] Add asset tag setting

Add SMBIOS asset tag as a named setting.

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

src/include/gpxe/smbios.h

 /** SMBIOS system information structure type */
 #define SMBIOS_TYPE_SYSTEM_INFORMATION 1
 
+/** SMBIOS enclosure information structure */
+struct smbios_enclosure_information {
+	/** SMBIOS structure header */
+	struct smbios_header header;
+	/** Manufacturer string */
+	uint8_t manufacturer;
+	/** Type string */
+	uint8_t type;
+	/** Version string */
+	uint8_t version;
+	/** Serial number string */
+	uint8_t serial;
+	/** Asset tag */
+	uint8_t asset_tag;
+} __attribute__ (( packed ));
+
+/** SMBIOS enclosure information structure type */
+#define SMBIOS_TYPE_ENCLOSURE_INFORMATION 3
+
 /**
  * SMBIOS entry point descriptor
  *

src/interface/smbios/smbios_settings.c

 					   serial ),
 		.type = &setting_type_string,
 	},
+	{
+		.name = "asset",
+		.description = "Asset tag",
+		.tag = SMBIOS_STRING_TAG ( SMBIOS_TYPE_ENCLOSURE_INFORMATION,
+					   struct smbios_enclosure_information,
+					   asset_tag ),
+		.type = &setting_type_string,
+	},
 };