MIPS: Lantiq: Add PCI controller support.

MIPS: Lantiq: Add PCI controller support.

The Lantiq family of SoCs have a EBU (External Bus Unit). This patch adds
the driver that allows us to use the EBU as a PCI controller. In order for
PCI to work the EBU is set to endianess swap all the data. In addition we
need to make use of SWAP_IO_SPACE for device->host DMA to work.

The clock of the PCI works in several modes (internal/external). If this
is not configured correctly the SoC will hang.

Signed-off-by: John Crispin <[email protected]>
Signed-off-by: Ralph Hempel <[email protected]>
Cc: [email protected]
Patchwork: https://patchwork.linux-mips.org/patch/2250/
Signed-off-by: Ralf Baechle <[email protected]>