drivers: espi: espi_mchp_xec: Fix the VW change check time

Adjusted the VW change check timings:
- Polling time changed from 100 uSec to 1 uSec.
- Timeout value changed from 10 mSec to 1 mSec.

This is to achieve the lowest possible pulse width for SCI VW in S0,
while ensuring that the VW change check is still reliable for S0iX
where SoC may take longer to process upstream events.

Also added -ETIMEDOUT error when failure.

Signed-off-by: Aditya Bhutada <aditya.bhutada@intel.com>