testsuite: utils: use IPI instead of int instruction for testing on x86

For x86, make the testing purpose trigger_irq() function to send
interrupt processor interrupt to CPU by APIC, instead of executing
INT instruction. Doing this because:
1. It can be controlled by irq lock, more close to trigger irq.
2. We don't need to hardcode the interrupt vector.

Signed-off-by: Enjia Mai <enjiax.mai@intel.com>