igb_uio: issue FLR during open and release of device file

igb_uio: issue FLR during open and release of device file

Set UIO info device file operations open and release. Call pci reset
function inside open and release to clear device state at start and end.
Copied this behaviour from vfio_pci kernel module code. With this patch,
it is not mandatory to issue FLR by PMD's during init and close.

Bus master enable and disable are added in open and release respectively
to take care of device DMA.

Signed-off-by: Shijith Thotton <shijith.thotton@caviumnetworks.com>
Reviewed-by: Jianfeng Tan <jianfeng.tan@intel.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Gregory Etelson <gregory@weka.io>