ixgbe: Add missing destroy_workqueue() on error in ixgbe_init_module()

Add the missing destroy_workqueue() before return from
ixgbe_init_module() in the error handling case.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>