hv: pirq: clean up irq handlers

There are several similar irq handlers with confusing function names and it's
not friendly to call update_irq_handler() to update a proper handler after
request_irq().

With this commit, a single generic irq handler is being used, in which, no lock
need to be acquired because our design could guarantee there is no concurrent
irq handling and irq handler request/free.
A flags field is added to irq_desc struct to select the proper processing flow
for an irq. Irqflags is defined as follows:
 IRQF_NONE       (0U)
 IRQF_LEVEL      (1U << 1U)       /* 1: level trigger; 0: edge trigger */
 IRQF_PT         (1U << 2U)       /* 1: for passthrough dev */

Because we have only one irq handler, update_irq_handler() should be replace by
set_irq_trigger_mode(), whichs set trigger mode flag of a certian irq.
Accordingly, the code where called update_irq_handler() need to be updated.

Signed-off-by: Yan, Like <like.yan@intel.com>
Acked-by: Anthony Xu <anthony.xu@intel.com>

hypervisor/common/ptdev.c

@@ -136,7 +136,7 @@ ptdev_activate_entry(struct ptdev_remapping_info *entry, uint32_t phys_irq)
 
 	/* register and allocate host vector/irq */
 	retval = request_irq(phys_irq, ptdev_interrupt_handler,
-				         (void *)entry);
+		             (void *)entry, IRQF_PT);
 
 	ASSERT(retval >= 0, "dev register failed");
 	entry->allocated_pirq = (uint32_t)retval;