hw/riscv: define capabilities of CBQRI controllers

Define structs to represent the hardware capabilities of capacity and
bandwidth controllers according to the RISC-V Capacity and Bandwidth QoS
Register Interface (CBQRI).

Link: https://github.com/riscv-non-isa/riscv-cbqri/blob/main/riscv-cbqri.pdf


Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Signed-off-by: Drew Fustini <dfustini@baylibre.com>