lib: sbi_pmu: check for index overflows

sbi_pmu_ctr_cfg_match() receives data from a lower privilege level mode.
We must catch maliciously wrong values.

We already check against total_ctrs. But we do not check that total_ctrs is
less than SBI_PMU_HW_CTR_MAX + SBI_PMU_FW_CTR_MAX.

Check that the number of hardware counters is in the valid range.

Addresses-Coverity-ID: 1566114 Out-of-bounds write
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>