tcl/target: Move GigaDevice configs into vendor directory

Move the configuration files into a dedicated vendor folder as required
by the developer guidelines.

Change-Id: I9ed39e32b6281a9cb8510914690f3f7751b795c8
Signed-off-by: Marc Schink <dev@zapb.de>
Reviewed-on: https://review.openocd.org/c/openocd/+/9271
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

src/helper/startup.tcl

@@ -47,7 +47,7 @@ proc find {filename} {
 		return $t
 	}
 
-	foreach vendor {nordic ti sifive st} {
+	foreach vendor {gigadevice nordic sifive st ti} {
 		# - path/to/a/certain/config_file
 		# replaced either with
 		# - path/to/a/certain/${vendor}/config_file