lenovo: Hide SMBIOS config

It's derived from EEPROM on Lenovo machines and not from user config
which is ignored.

Change-Id: I54fb76a3160e47cd36d33d2937c4bfaddcd36a69
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/7055
Tested-by: build bot (Jenkins)
Reviewed-by: Nicolas Reinecke <nr@das-labor.org>

src/drivers/i2c/at24rf08c/Kconfig

@@ -0,0 +1,7 @@
+if VENDOR_LENOVO
+
+config SMBIOS_PROVIDED_BY_MOBO
+	bool
+	default y
+
+endif

src/drivers/i2c/at24rf08c/lenovo_serials.c

@@ -213,3 +213,8 @@ const char *smbios_mainboard_bios_version(void)
 	s = strconcat("CBET4000 ", coreboot_version);
 	return s;
 }
+
+const char *smbios_mainboard_manufacturer(void)
+{
+	return "LENOVO";
+}