Staging: et13x: kill off TXMAC_ERR_INT_t

This completes the structures within the txmac block so we can now
propogate a name change and type removal up a layer and clean up TXMAC as
well

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>