fix: Set max_size to fill remainder of 512kB eFlash

Author: pqcfox

tockloader/board_interface.py

@@ -298,8 +298,9 @@ class BoardInterface:
             "no_attribute_table": True,
             "address_translator": lambda addr: addr - 0x20010000,
             "flash_file": {
-                # Set to the maximum flash size.
-                "max_size": 0x00100000,
+                # Set to the half of maximum flash size, to keep image sizes smaller
+                # (also ensures room for data at end of flash).
+                "max_size": 0x00070000,
             },
         },
     }