[Qemu-riscv] RISC-V: Include ROM in QEMU

[Alistair Francis]

Hello,

As a test of the waters, how would the QEMU community feel about
including the RISC-V OpenSBI project as a ROM submodule?

The idea would be to have OpenSBI (similar to ATF for ARM and a BIOS
for x86) included by default to simplify the QEMU RISC-V boot process
for users. This would remove the requirement for users/developers to
build a RISC-V firmware. The goal here is to allow people to just
download and run their kernel as easily as they currently do for x86.

We would make sure that it can be disabled! That is users/developers
can use their own (or none) if they want to. The idea here is just to
simplify the boot process, not lock anyone out.

Alistair