env_eeprom: Move conditional compilation to Makefile

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/common/Makefile b/common/Makefile
index a9a02b2..9001237 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -51,7 +51,7 @@
 COBJS-y += environment.o
 COBJS-y += env_common.o
 COBJS-y += env_dataflash.o
-COBJS-y += env_eeprom.o
+COBJS-$(CONFIG_ENV_IS_IN_EEPROM) += env_eeprom.o
 COBJS-y += env_flash.o
 COBJS-y += env_nand.o
 COBJS-y += env_nvram.o