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>
diff --git a/drivers/char/agp/ati-agp.c b/drivers/char/agp/ati-agp.c
index da7513d..2d46b71 100644
--- a/drivers/char/agp/ati-agp.c
+++ b/drivers/char/agp/ati-agp.c
@@ -213,6 +213,9 @@
 	temp = (temp & 0xfffff000);
 	ati_generic_private.registers = (volatile u8 __iomem *) ioremap(temp, 4096);
 
+	if (!ati_generic_private.registers)
+		return -ENOMEM;
+
 	if (is_r200())
 		pci_write_config_dword(agp_bridge->dev, ATI_RS100_IG_AGPMODE, 0x20000);
 	else