sky2: fix for Yukon FE (regression in 2.6.25)

The Yukon FE chip has a ram buffer therefore it needs the alignment
restriction and hang check workarounds.

Therefore:
  * Autodetect the prescence/absence of ram buffer
  * Rename the flag value to reflect this
  * Use it consistently (ie don't reread register)

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>