raw/ifpga/base: fix interrupt handler instance usage

raw/ifpga/base: fix interrupt handler instance usage

Interrupt handler copied to the local 'intr_handle' variable by value
before passing it to IRQ functions.
This leads IRQ functions update the local variable instead of
'ifpga_irq_handle'.

Instead, using 'intr_handle' local variable as pointer to
'ifpga_irq_handle' as intended.

Fixes: e0a1aafe2af9 ("raw/ifpga: introduce IRQ functions")
Cc: stable@dpdk.org
Signed-off-by: Wei Huang <wei.huang@intel.com>
Signed-off-by: Tianfei Zhang <tianfei.zhang@intel.com>
Acked-by: Rosen Xu <rosen.xu@intel.com>