samples: mei: don't wait on read completion upon write.

The original mei driver communication was strictly write command and
receive response flow, the completion of write was determined when
response was ready using select(). This paradigm is a long time not
true.  There can be write without a response and an unsolicited read.
The driver is capable of handling those.
Adjust also the sample code and remove select() on read() from the
write flow. Add select to the read flow to showcase how to do the
read with a timeout.

Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Link: https://lore.kernel.org/r/20210801072532.8668-1-tomas.winkler@intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>