usb: ehci: Fix a function name in comments

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

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Link: https://lore.kernel.org/r/20210925124920.1564-1-caihuoqing@baidu.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>