Introduce optimized iomemcpy function for copying from io memory.

Introduce optimized iomemcpy function for copying from io memory.

Reading from IO memory (pci rom or flash) is very slow, so add
   iomemcpy() which will yield during copy.  Use a 4 byte copy to
   optimize accesses.
Also, decompress cbfs data files from a temp memory buffer so that
   ulzma doesn't read from slow IO memory.