drivers/perf: riscv: Read upper bits of a firmware counter

drivers/perf: riscv: Read upper bits of a firmware counter

SBI v2.0 introduced a explicit function to read the upper 32 bits
for any firmware counter width that is longer than 32bits.
This is only applicable for RV32 where firmware counter can be
64 bit.

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20240420151741.962500-4-atishp@rivosinc.com
Signed-off-by: Anup Patel <anup@brainfault.org>