agp: balance ioremap checks

patchset against 2.6.23-rc3.
corrects missing ioremap return checks and balancing on iounmap calls, integrated changes per list
recommendations on the original set of patches..

Signed-off-by: Scott Thompson <postfail <at> hushmail.com>
Signed-off-by: Dave Airlie <airlied@linux.ie>
6 files changed