RISC-V: Move counter info definition to sbi header file

Counter info encoding format is defined by the SBI specificaiton.
KVM implementation of SBI PMU extension will also leverage this definition.
Move the definition to common sbi header file from the sbi pmu driver.

Signed-off-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20220711174632.4186047-5-atishp@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>