Setting global asic structure to point to different function
would cause problem in system where is multiple r300 cards
with different bus type.

r300_asic_pcie is just copy from r300_asic with gart tlb
functions replaced with pcie versions.
Signed-off-by: Pauli Nieminen <suokkos@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>