forcedeth endianness bugs

* misannotation: struct register_test members are actually host-endian
* bug: cpu_to_le64(n) >> 32 instead of cpu_to_le32(n >> 32) in setting
->bufhigh and similar for ->buflow (take low bits, _then_ convert to
little-endian, not the other way round).
* bug: setup_hw_rings() should not convert to little-endian at all (we
feed the result to writel(), not store in shared data structure), let
alone try to play with shifting and masking little-endian values.  Introduced
when setup_hw_rings() went in, screwed both 64bit case and the old code for
32bit rings it had replaced.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jeff Garzik <jeff@garzik.org>