sandbox: Correct cros-ec keyboard definition

The other boards got updated to the standard binding. Update sandbox as
well.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/sandbox/dts/sandbox.dts

@@ -73,10 +73,8 @@
 
 	cros-ec-keyb {
 		compatible = "google,cros-ec-keyb";
-		google,key-rows = <8>;
-		google,key-columns = <13>;
-		google,repeat-delay-ms = <240>;
-		google,repeat-rate-ms = <30>;
+		keypad,num-rows = <8>;
+		keypad,num-columns = <13>;
 		google,ghost-filter;
 		/*
 		 * Keymap entries take the form of 0xRRCCKKKK where