message: Adjust the NRF52840-DK's RAM window to match that of latest Tock master.
diff: MEMORY {
  FLASH (X) : ORIGIN = 0x00030000, LENGTH = 0x000D0000
  - RAM (W) : ORIGIN = 0x20004000, LENGTH = 62K
  + RAM (W) : ORIGIN = 0x20008000, LENGTH = 46K
  }
  TBF_HEADER_SIZE = 0x48;
  