Sscofpmf ISA extension introduces PMU counter overflow and filtering support. It introduces a read only `scountovf` csr that can be used to detect if a hart supports this extension at runtime. However, this feature is only useful if the hart already supports mcounteren and mcountinhibit. Add a dynamic detection mechanism and boot time print message if sscofpmf is present. Reviewed-by: Anup Patel <anup.patel@wdc.com> Reviewed-by: Bin Meng <bmeng.cn@gmail.com> Signed-off-by: Atish Patra <atish.patra@wdc.com>