common: kconfig: Correct a typo in SPL_LOAD_FIT

It should be FDT, not FTD.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Rick Chen <rick@andestech.com>
diff --git a/common/Kconfig.boot b/common/Kconfig.boot
index 5660822..71a215c 100644
--- a/common/Kconfig.boot
+++ b/common/Kconfig.boot
@@ -205,7 +205,7 @@
 
 	  This path has the following limitations:
 
-	  1. "loadables" images, other than FTDs, which do not have a "load"
+	  1. "loadables" images, other than FDTs, which do not have a "load"
 	     property will not be loaded. This limitation also applies to FPGA
 	     images with the correct "compatible" string.
 	  2. For FPGA images, only the "compatible" = "u-boot,fpga-legacy"