This fixes the problem of reference count leak if
igbuio_pci_enable_interrupts fails.
Also, replace mutex and integer with a kernel atomic counter.
This is standard pattern for kernel devices.
Fixes: 19685d5aa79c ("igb_uio: allow multi-process access")
Cc: stable@dpdk.org
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>
ab856f2947