netxen: fix byte-swapping in tx and rx

Here's the reworked patch.

This cleans up some unnecessary byte-swapping while setting up tx and
interpreting rx desc. The 64 bit rx status data should be converted
to host endian format only once and the macros just need to extract
bitfields.

This saves a spate of interrupts on pseries blades caused by buggy
(non) processing rx status ring.

Signed-off-by: Dhananjay Phadke <dhananjay@netxen.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>