MIPS: OCTEON: don't set octeon_dma_bar_type if PCI is disabled

Don't set octeon_dma_bar_type if PCI is disabled. This avoids creation
of the MSI irqchip later on, and saves a bit of memory.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Fixes: a214720c ("Disable MSI also when pcie-octeon.pcie_disable on")
Cc: stable@vger.kernel.org # v3.3+
Cc: linux-mips@vger.kernel.org