[PATCH] e1000: fix TX timout hang regression for 82542rev3

[PATCH] e1000: fix TX timout hang regression for 82542rev3

Commit bd99e5599733d78f23b6908d7cba3c6a73b0239d (oct. 5 2005) introduced
partial Multiqueue support for e1000 which broke macro smartness in setting
up head/tail registers for 82542 rev3 chipsets, making these adapters
completely non-working since 2.6.15.

This commit sets the proper head and tail registers for read and write
descriptor rings. Ths fix was tested on an 82542 rev3 NIC and newer NICs.

Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>