oneplus-hotdogb: Add OnePlus 7T device pkg

This MR adds OnePlus 7T device, interestingly only guacamole is currently in pmaports so maybe there is a reason why? I haven't tested full boot yet, UFS storage seems flaky on 6.4 meinline kernel but at least debug-shell over usb network works.

The wiki entry seems to bundle all OP 7's together https://wiki.postmarketos.org/wiki/OnePlus_7_(oneplus-guacamoleb)