TARGET/ARM920T: fix return value

Function arm920t_write_memory() default return value
should be ERROR_OK.
All cases of local errors are handled immediately and
not further propagated.

Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>

src/target/arm920t.c

@@ -711,7 +711,7 @@ int arm920t_write_memory(struct target *target, uint32_t address,
 		}
 	}
 
-	return retval;
+	return ERROR_OK;
 }
 
 // EXPORTED to FA256