Add: RISC-V support

[kassane]

Especially RISC-V64.

There is some expectation of adding support for the new RISCV architecture, even though it is an emulated environment for example QEMU.

[VictorElHajj]

👍 This has been an issue for myself as well

[petterreinholdtsen]

According to https://bugs.debian.org/1016623, /proc/cpuinfo can look like this:

processor	: 0
hart		: 2
isa		: rv64imafdc
mmu		: sv39
uarch		: sifive,bullet0

processor	: 1
hart		: 1
isa		: rv64imafdc
mmu		: sv39
uarch		: sifive,bullet0

processor	: 2
hart		: 3
isa		: rv64imafdc
mmu		: sv39
uarch		: sifive,bullet0

processor	: 3
hart		: 4
isa		: rv64imafdc
mmu		: sv39
uarch		: sifive,bullet0

[leuc]

cat /proc/device-tree/model
StarFive VisionFive V2

cat /proc/device-tree/compatible
starfive,visionfive-v2starfive,jh7110

cat /proc/device-tree/serial-number
VF7110A1-2250-D008E000-00000824

cat /proc/cpuinfo
processor	: 0
hart		: 1
isa		: rv64imafdc
mmu		: sv39
uarch		: sifive,u74-mc

processor	: 1
hart		: 2
isa		: rv64imafdc
mmu		: sv39
uarch		: sifive,u74-mc

processor	: 2
hart		: 3
isa		: rv64imafdc
mmu		: sv39
uarch		: sifive,u74-mc

processor	: 3
hart		: 4
isa		: rv64imafdc
mmu		: sv39
uarch		: sifive,u74-mc

[enh-google]

#190