Adds a new default option: SPIKE. This builds the support for the Spike platform.
Switch toolchain dependency from riscv64-gcc to riscv64-none-elf-gcc.
This release has:
Relocation lottery in reference firmwares Preferred boot HART field in fw_dynamic_info Platform specific optional way to specify MISA Hypervisor v0.5 specification support SBI v0.2 TIME extension SBI v0.2 IPI extension SBI v0.2 RFENCE extension T-HEAD C910 platform support HART exit path support Dynamic creation of IPI events Dynamic registration of SBI extensions Removed qemu/sifive_u platform support Spike platform support Print MIDELEG and MEDELEG in boot prints