mkimage: Refactor imagetool_get_source_date to take command name

So we can use imagetool_get_source_date() from callers who do not have
the image tool params struct, just pass in the command name for the error
message.

Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Reviewed-by: Simon Glass <sjg@chromum.org>
diff --git a/tools/default_image.c b/tools/default_image.c
index 4abff45..4b7d1ed 100644
--- a/tools/default_image.c
+++ b/tools/default_image.c
@@ -100,7 +100,7 @@
 				sizeof(image_header_t)),
 			sbuf->st_size - sizeof(image_header_t));
 
-	time = imagetool_get_source_date(params, sbuf->st_mtime);
+	time = imagetool_get_source_date(params->cmdname, sbuf->st_mtime);
 	ep = params->ep;
 	addr = params->addr;
 
diff --git a/tools/fit_image.c b/tools/fit_image.c
index e55a894..6f09a66 100644
--- a/tools/fit_image.c
+++ b/tools/fit_image.c
@@ -51,7 +51,8 @@
 
 	/* for first image creation, add a timestamp at offset 0 i.e., root  */
 	if (params->datafile) {
-		time_t time = imagetool_get_source_date(params, sbuf.st_mtime);
+		time_t time = imagetool_get_source_date(params->cmdname,
+							sbuf.st_mtime);
 		ret = fit_set_timestamp(ptr, 0, time);
 	}
 
diff --git a/tools/imagetool.c b/tools/imagetool.c
index a4e39b2..b3e628f 100644
--- a/tools/imagetool.c
+++ b/tools/imagetool.c
@@ -116,7 +116,7 @@
 }
 
 time_t imagetool_get_source_date(
-	 struct image_tool_params *params,
+	 const char *cmdname,
 	 time_t fallback)
 {
 	char *source_date_epoch = getenv("SOURCE_DATE_EPOCH");
@@ -128,7 +128,7 @@
 
 	if (gmtime(&time) == NULL) {
 		fprintf(stderr, "%s: SOURCE_DATE_EPOCH is not valid\n",
-			params->cmdname);
+			cmdname);
 		time = 0;
 	}
 
diff --git a/tools/imagetool.h b/tools/imagetool.h
index d191b9c..63c08eb 100644
--- a/tools/imagetool.h
+++ b/tools/imagetool.h
@@ -216,12 +216,12 @@
  * an error message if SOURCE_DATE_EPOCH contains an invalid value and returns
  * 0.
  *
- * @params:	mkimage parameters
+ * @cmdname:	command name
  * @fallback:	timestamp to use if SOURCE_DATE_EPOCH isn't set
  * @return timestamp based on SOURCE_DATE_EPOCH
  */
 time_t imagetool_get_source_date(
-	struct image_tool_params *params,
+	const char *cmdname,
 	time_t fallback);
 
 /*