Doc: z8530book: Fix typo in API-z8530-sync-txdma-open.html

This patch fix a spelling typo found in API-z8530-sync-txdma-open.html.
It is because this file was generated from comment in source,
I have to fix comment in source.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wan/z85230.c

@@ -1044,7 +1044,7 @@ EXPORT_SYMBOL(z8530_sync_dma_close);
  *	@dev: The network device to attach
  *	@c: The Z8530 channel to configure in sync DMA mode.
  *
- *	Set up a Z85x30 device for synchronous DMA tranmission. One
+ *	Set up a Z85x30 device for synchronous DMA transmission. One
  *	ISA DMA channel must be available for this to work. The receive
  *	side is run in PIO mode, but then it has the bigger FIFO.
  */