cmd: fdt: Align checksign parameter names in help text

The help text references 'addr' as an optional key start address,
but the explanation references the same as 'start', make sure they
both read as 'addr'. Also update the abbreviated 'addr' in the
explanation to 'address'.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/cmd/fdt.c b/cmd/fdt.c
index f257bee..279dad9 100644
--- a/cmd/fdt.c
+++ b/cmd/fdt.c
@@ -1138,8 +1138,8 @@
 	"                                        <start>/<size> - initrd start addr/size\n"
 #if defined(CONFIG_FIT_SIGNATURE)
 	"fdt checksign [<addr>]              - check FIT signature\n"
-	"                                        <start> - addr of key blob\n"
-	"                                                  default gd->fdt_blob\n"
+	"                                      <addr> - address of key blob\n"
+	"                                               default gd->fdt_blob\n"
 #endif
 	"NOTE: Dereference aliases by omitting the leading '/', "
 		"e.g. fdt print ethernet0.";