netdev: uniquify the tx_timeout name

there's several drivers that have use "tx_timeout" for the .. tx
timeout function.  All fine with that, they're static, however for
doing stats on how often which driver hits the timeout it's a tad
unfortunate. The patch below gives the ones I found in the
kerneloops.org database unique names.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>