netutils/netinit: Support the NETINIT_MACADDR.

[13627105546]

Note: Please adhere to Contributing Guidelines.

Summary

• Why: In some embedded scenarios, the MAC address is stored in a specific location (e.g., a file like device.info, OTP, or NVM) rather than being generated from a unique ID or fixed at compile time. A mechanism is needed to allow netinit to retrieve this MAC address from the board logic.
• What: This commit adds a new configuration option CONFIG_NETINIT_MACADDR. When enabled, netinit attempts to fetch the MAC address via boardctl(BOARDIOC_MACADDR, ...). This allows board-specific logic to provide the correct MAC address during network initialization.

Impact

• Users: Users can now select CONFIG_NETINIT_MACADDR in Kconfig if their board supports providing a MAC address via boardctl.
• Build: Introduces CONFIG_NETINIT_MACADDR. No impact on existing builds unless this new option is enabled.
• Hardware: Requires board-level support for BOARDIOC_MACADDR command in board_ioctl if this feature is enabled.
• Compatibility: Backward compatible. Existing MAC address initialization methods (UIDMAC, ETHERNET, etc.) remain unchanged.

Testing

• Verification:
• Verified that the code compiles successfully with CONFIG_NETINIT_MACADDR enabled.
• Verified that checkpatch.sh passes for the modified files.
• Target: Verified on local hardware platform where boardctl is implemented to read MAC address from device storage.

[simbit18]

@13627105546 Please fix

../nuttx/tools/checkpatch.sh -c -u -m -g b0b90ac72886a7d2ee8d9a16e057a4b2c801984e..HEAD
❌ Missing git commit message
Used config files:
    1: .codespellrc
Some checks failed. For contributing guidelines, see:
  https://github.com/apache/nuttx/blob/master/CONTRIBUTING.md
Error: Process completed with exit code 1.

[acassis]

@13627105546 this is a new Feature, please add a Documentation to it

[13627105546]

@13627105546 this is a new Feature, please add a Documentation to it

I have supplemented the documentation (apache/nuttx#18031) with Documentation/reference/user/13_boardctl.rst