qca4019: Add Meraki Z3

qca4019: Add Meraki Z3

Add board file for Meraki Z3/Z3C router

Board file was extracted from the latest Meraki firmware
for this device (mid 2025).

board.json:
```
[
  {
    "names": ["bus=ahb,bmi-chip-id=0,bmi-board-id=20,variant=Meraki-Z3"],
    "data": "board-data/boardData_1_0_IPQ4019_DK04_2G_Z3.bin"
  },
  {
    "names": ["bus=ahb,bmi-chip-id=0,bmi-board-id=21,variant=Meraki-Z3"],
    "data": "board-data/boardData_1_0_IPQ4019_DK04_5G_Z3.bin"
  }
]
```

Signed-off-by: Hal Martin <[email protected]>
Link: https://github.com/openwrt/firmware_qca-wireless/pull/111
Signed-off-by: Robert Marko <[email protected]>