soundwire: qcom: update register read/write routine

In the existing code every soundwire register read and register write
are kinda blocked. Each of these are using a special command id that
generates interrupt after it successfully finishes. This is really
overhead, limiting and not really necessary unless we are doing
something special.

We can simply read/write the fifo that should also give exactly
what we need! This will also allow to read/write registers in
interrupt context, which was not possible with the special
command approach.

With previous approach number of interrupts generated
after enumeration are around 130:
$ cat /proc/interrupts  | grep soundwire
 21: 130 0 0 0 0 0 0 0 GICv3 234 Edge      soundwire

after this patch they are just 3 interrupts
$ cat /proc/interrupts  | grep soundwire
 21: 3 0 0 0 0 0 0 0 GICv3 234 Edge      soundwire

This has significantly not only reduced interrupting CPU during enumeration
but also during streaming!

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210330144719.13284-6-srinivas.kandagatla@linaro.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>