raw/ifpga: introduce IRQ functions

raw/ifpga: introduce IRQ functions

Introducing new register and unregister API for ifpga interrupt.
1. register FME and AFU interrupt
   ifpga_register_msix_irq()

2. unregister FME and AFU interrupt
   ifpga_unregister_msix_irq()

On PAC N3000 card, there is one PCIe MSIX interrupt for FME management,
like the error report, thermal management, we use this interrupt in
ifpga_rawdev device driver. on the other hand, there are about 4 PCIe
MSIX interrupts are reserved for AFU which end-user can use those
interrupts in their AFU logic design. End-user can use those APIs to
register interrupt handler in their AFU drivers.

Signed-off-by: Tianfei Zhang <tianfei.zhang@intel.com>
Signed-off-by: Andy Pei <andy.pei@intel.com>