Add board "Lilygo TTGO T7 V1.5"

[kaessert]

This PR adds support for the Lilygo TTGO T7 V1.5 baord. It's my first pr of that kind so please be gentle with me :)

[github-actions]

Hello @kaessert, and thank you very much for your first pull request to the Zephyr project!
Our Continuous Integration pipeline will execute a series of checks on your Pull Request commit messages and code, and you are expected to address any failures by updating the PR. Please take a look at our commit message guidelines to find out how to format your commit messages, and at our contribution workflow to understand how to update your Pull Request. If you haven't already, please make sure to review the project's Contributor Expectations and update (by amending and force-pushing the commits) your pull request if necessary.
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[kaessert]

Thank you so much for your review @nordicjm ! I addressed the comments.

[kaessert]

Thank you so much for your patience 🙏

[nordicjm]

Can you squash the commits down to one commit?

[kaessert]

@nordicjm Sure, squashed

[kaessert]

Found and fixed an error in my appcpu-defconfig. Tests should pass now.

[github-actions]

Hi @kaessert!
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!

To celebrate this milestone and showcase your contribution, we'd love to award you the Zephyr Technical Contributor badge. If you're interested, please claim your badge by filling out this form: Claim Your Zephyr Badge.

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

[kaessert]

Thanks for your support everybody!