Correct SPL uses of CMD_BOOTM_PRE_LOAD

This converts 2 usages of this option to the non-SPL form, since there is
no SPL_CMD_BOOTM_PRE_LOAD defined in Kconfig

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/boot/bootm.c b/boot/bootm.c
index e6715ae..56b82bb 100644
--- a/boot/bootm.c
+++ b/boot/bootm.c
@@ -100,7 +100,7 @@
 	ulong data_addr = bootm_data_addr(argc, argv);
 	int ret = 0;
 
-	if (CONFIG_IS_ENABLED(CMD_BOOTM_PRE_LOAD))
+	if (IS_ENABLED(CONFIG_CMD_BOOTM_PRE_LOAD))
 		ret = image_pre_load(data_addr);
 
 	if (ret)
@@ -893,7 +893,7 @@
 					      &fit_uname_config,
 					      &fit_uname_kernel);
 
-	if (CONFIG_IS_ENABLED(CMD_BOOTM_PRE_LOAD))
+	if (IS_ENABLED(CONFIG_CMD_BOOTM_PRE_LOAD))
 		img_addr += image_load_offset;
 
 	bootstage_mark(BOOTSTAGE_ID_CHECK_MAGIC);