ASoC: Add spi hw read function for 16 addr 8 data mode for ad193x fix

ASoC: Add spi hw read function for 16 addr 8 data mode for ad193x fix

[This will be used by the ad193x driver to fix the fact that the
original author of the driver put a bodge for their particular chip into
a the generic ASoC register I/O abstraction layer which looked like an
obvious bug which ended up getting fixed in 3.0.  Sadly there were no
comments documenting what was going on.  A minimally invasive correction
to the driver is to remove the register cache support and go direct to
the hardware all the time so we're adding a new feature -- broonie]

Signed-off-by: Scott Jiang <scott.jiang.linux@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>