board: sifive: unmatched: add initial support for a platform ID EEPROM

Add initial support for the PCB description EEPROM for SiFive HiFive
Unmatched boards.

This implementation is refactored based on Paul Walmsley's porting and
adopt the suggestions from David Abdurachmanov.

Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Signed-off-by: David Abdurachmanov <david.abdurachmanov@sifive.com>
Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
diff --git a/include/configs/sifive-unmatched.h b/include/configs/sifive-unmatched.h
index 80cfd41..d63a5f6 100644
--- a/include/configs/sifive-unmatched.h
+++ b/include/configs/sifive-unmatched.h
@@ -81,4 +81,10 @@
 	"fdt addr ${fdtcontroladdr};"
 #endif /* CONFIG_SPL_BUILD */
 
+#define CONFIG_SYS_EEPROM_BUS_NUM		0
+#define CONFIG_SYS_I2C_EEPROM_ADDR		0x54
+#define CONFIG_SYS_I2C_EEPROM_ADDR_LEN		0x1
+
+#define CONFIG_ID_EEPROM
+
 #endif /* __SIFIVE_UNMATCHED_H */