i945: make PCIe link wait sensible

Waiting for (a & 4) == 3 to become true proves futile
unless you're searching for defective hardware or
neutrino impact.

While I'm not 100% sure that this is the actual intent
(no data-sheets at hand, and the public ones are unhelpful
as usual), it's the likely correct version and it's also
boot-tested on intel/d945gclf.

While at it, replace register number with the name found
in the public datasheet.

Change-Id: I4b87001967a2013e0089806e8cd606d5ee81b0d9
Found-by: Coverity Scan
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/6575
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>