tools/libxl: Switch irq to unsigned int

tools/libxl: Switch irq to unsigned int

The PCI device irq is read with fscanf(%u).  Switch the irq variable to
unsigned int to match.

Linux driver/pci/pci-sysfs.c:irq_show() uses %u to print the value.

However, unsigned int irq doesn't compile because of:
error: pointer targets in passing argument 4 of 'xc_physdev_map_pirq' differ in signedness [-Werror=pointer-sign]

Add int pirq to provide the desired type instead of re-using irq.

Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
Reviewed-by: Anthony PERARD <anthony.perard@vates.tech>