lib: sbi: Add SSE support for PMU events

Add SSE callbacks registration to PMU driver in order to disable
interrupt delegation for PMU interrupts. When interrupts are
undelegated send the PMU SSE event upon LCOFIP IRQ.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>