New port: sysutils/u-boot-qemu-riscv64
Add a u-boot port for QEMU's 64-bit RISC-V config. A simple u-boot
payload is provided that can be specified on the command line. It runs
in supervisor mode, and should be paired with OpenSBI.
Reviewed by: manu
Approved by: u-boot (manu)
Differential Revision: https://reviews.freebsd.org/D25737