Correct SPL use of FSL_MC_ENET

This converts 1 usage of this option to the non-SPL form, since there is
no SPL_FSL_MC_ENET defined in Kconfig

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/traverse/ten64/ten64.c b/board/traverse/ten64/ten64.c
index d3ff1d1..13aafb5 100644
--- a/board/traverse/ten64/ten64.c
+++ b/board/traverse/ten64/ten64.c
@@ -229,7 +229,7 @@
 
 	fdt_fsl_mc_fixup_iommu_map_entry(blob);
 
-	if (CONFIG_IS_ENABLED(FSL_MC_ENET))
+	if (IS_ENABLED(CONFIG_FSL_MC_ENET))
 		fdt_fixup_board_enet(blob);
 
 	fdt_fixup_icid(blob);