serdev: Replace poll loop by readx_poll_timeout() macro

The readx_poll_timeout() consolidates the necessary code under
macro. Replace current code with it.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20221114151813.37294-1-andriy.shevchenko@linux.intel.com


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