[sound/oss i810] add MMIO DSP support

Enclosed is a patch for the i810_audio OSS driver to support using
memory-mapped I/O for those chipsets that support it.

 o Added a family of macros -- I810_IOREADx() and I810_IOWRITEx() -- that
key off the existing card->use_mmio flag to select between using readx/writex
or inx/outx for I/O operations.

 o Converted existing inx/outx invocations to use
I810_IOREADx/I810_IOWRITEx instead.

 o Changed GET_CIV(), GET_LVI, and CIV_TO_LVI() not only to use
I810_IOREADx/I810_IOWRITEx but also to take "card" (i.e. struct i810_card)
paramter.

 o Removed check for "Pure MMIO interfaces" in i810_probe() -- replaced w/
(relocated) check for no I/O resources available.