[PATCH] orinoco: refactor and clean up Tx error handling

The result of orinoco_xmit() can be OK, dropped packet and busy
transmitter.  Rename labels accordingly.  Increment stats->tx_errors in
one place.  Increment stats->tx_dropped - nobody is doing it for us.

Signed-off-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>