binman: bintool: Change make target arg type from string to list

The argument type of `build_from_git` was changed from string to list
in d71e7116997f14097735f04cc7847f0a68dbc485.

This commit adapts the argument type of all bintools using this
function.

Signed-off-by: Lukas Funke <lukas.funke@weidmueller.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/btool/bootgen.py b/tools/binman/btool/bootgen.py
index f2ca552..1bc9f0a 100644
--- a/tools/binman/btool/bootgen.py
+++ b/tools/binman/btool/bootgen.py
@@ -132,6 +132,6 @@
 
         result = self.build_from_git(
             'https://github.com/Xilinx/bootgen',
-            'all',
+            ['all'],
             'bootgen')
         return result