lib: sbi_pmu: keep overflow interrupt of stopped hpm counter disabled

After the hardware hpm counter is stopped, it should not raise any new
interrupt as it is already stopped. So add the hw_counter_disable_irq
callback to allow the custom pmu device to control this behavior.

Signed-off-by: Inochi Amaoto <inochiama@outlook.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Anup Patel <anup@brainfault.org>
Tested-by: Samuel Holland <samuel@sholland.org>