MIPS HIGHMEM fixes for cache aliasing and non-DMA I/O.

MIPS HIGHMEM fixes for cache aliasing and non-DMA I/O.

This patch fixes MIPS HIGHMEM for cache aliasing and non-DMA device
I/O. It does the following:

1.  Uses only colored page addresses while allocating by kmap*(),
    page address in HIGHMEM zone matches a kernel address by color.
    It allows easy re-allocation before flushing cache.
    It does it for kmap() and kmap_atomic().

2.  Fixes instruction cache flush by right color address via
    kmap_coherent() in case of I-cache aliasing.

3.  Flushes D-cache before page is provided for process as I-page.
    It is required for swapped-in pages in case of non-DMA I/O.

4.  Some optimization is done... more comes.

Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>