disk: convert CONFIG_ISO_PARTITION to Kconfig

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Signed-off-by: Patrick Delaunay <patrick.delaunay73@gmail.com>
diff --git a/configs/dbau1500_defconfig b/configs/dbau1500_defconfig
index f447aa6..26f6da0 100644
--- a/configs/dbau1500_defconfig
+++ b/configs/dbau1500_defconfig
@@ -13,3 +13,4 @@
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_CMD_DHCP=y
 CONFIG_MAC_PARTITION=y
+# CONFIG_ISO_PARTITION is not set