igbvf: Check for error on dma_map_single call

Ignoring the return value from a call to the kernel dma_map API functions
can cause data corruption and system instability.  Check the return value
and take appropriate action.

Signed-off-by: Greg Rose <gregory.v.rose@intel.com>
Tested-by: Sibai Li <sibai.li@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>