net: fddi: skfp: Fix a function name in comments

Use dma_map_single() instead of pci_map_single(),
because only dma_map_single() is called here.

Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>