profiles: Use the rpi64 board for the rpi4-b device definition

This is necessary to report the test results properly to the qa-report-app.

Currently, the results for arm64-uboot and arm64-rpi64 are both reported for uboot and the last one to finish overwrites the results of the other. This patch makes sure the board is correctly set to rpi64 when submitting the tests metadata to LAVA.