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/MSI_Primo73_defconfig b/configs/MSI_Primo73_defconfig
index 7af1e06..7f34831 100644
--- a/configs/MSI_Primo73_defconfig
+++ b/configs/MSI_Primo73_defconfig
@@ -15,3 +15,4 @@
 # CONFIG_CMD_FLASH is not set
 # CONFIG_CMD_FPGA is not set
 # CONFIG_SPL_DOS_PARTITION is not set
+# CONFIG_SPL_ISO_PARTITION is not set