[AGPGART] Fix wrong ID in via-agp.c

there is a wrong id in drivers/char/agp/via-agp.c
#define PCI_DEVICE_ID_VIA_CX700         0x8324
It must be 0x0324

Notice that PCI_DEVICE_ID_VIA_CX700 is also used in
drivers/i2c/busses/i2c-viapro.c and
drivers/ide/pci/via82cxxx.c

So, I think that constant must be renamed to avoid conflicting.
I attached a proposed patch.

Signed-off-by: Dave Jones <davej@redhat.com>