binman: Rename state.GetFdts()

This function name conflicts with Entry.GetFdts() which has a different
purpose. Rename it to avoid confusion. Also update a stale comment
relating to this function.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/state.py b/tools/binman/state.py
index 5b9e005..77c7024 100644
--- a/tools/binman/state.py
+++ b/tools/binman/state.py
@@ -117,8 +117,8 @@
 def Prepare(images, dtb):
     """Get device tree files ready for use
 
-    This sets up a set of device tree files that can be retrieved by GetFdts().
-    At present there is only one, that for U-Boot proper.
+    This sets up a set of device tree files that can be retrieved by
+    GetAllFdts(). This includes U-Boot proper and any SPL device trees.
 
     Args:
         images: List of images being used
@@ -152,7 +152,7 @@
             other_dtb = fdt.FdtScan(out_fname)
             fdt_files[other_fname] = other_dtb
 
-def GetFdts():
+def GetAllFdts():
     """Yield all device tree files being used by binman
 
     Yields: