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/plutux_defconfig b/configs/plutux_defconfig
index 0b1de08..c518395 100644
--- a/configs/plutux_defconfig
+++ b/configs/plutux_defconfig
@@ -19,6 +19,7 @@
 # CONFIG_CMD_NFS is not set
 CONFIG_CMD_EXT4_WRITE=y
 # CONFIG_SPL_DOS_PARTITION is not set
+# CONFIG_SPL_ISO_PARTITION is not set
 CONFIG_SPL_DM=y
 # CONFIG_BLK is not set
 # CONFIG_DM_MMC_OPS is not set