boards: ezurio: Fix FEM name for BL654PA DVK

[randyscott]

For Kconfig auto-configuration of the FEM in the MPSL, the node in the device tree MUST be named "nrf_radio_fem".

[github-actions]

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[github-actions]

Hi @randyscott!
Congratulations on getting your very first Zephyr pull request merged 🎉🥳. This is a fantastic achievement, and we're thrilled to have you as part of our community!

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Thank you for your valuable input, and we look forward to seeing more of your contributions in the future! 🪁