drm/amdkfd: Check int source id for utcl2 poison event

Traditional utcl2 fault_status polling does not
work in SRIOV environment. The polling of fault
status register from guest side will be dropped
by hardware.

Driver should switch to check utcl2 interrupt
source id to identify utcl2 poison event. It is
set to 1 when poisoned data interrupts are
signaled.

v2: drop the unused local variable (Tao)

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>