lib: sbi: Remove MCOUNTEREN and SCOUNTEREN hart features

If a hart implements privileged spec v1.10 (or higher) then we can
safely assume that [m|s]counteren CSR are present and we don't need
MCOUNTEREN and SCOUNTEREN as hart features.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>