driver: espi: Enable espi uart port sirq based on uart mapping.

Espi has three uart port from 0 to 2 and uart sirq need to enabled for
the port which is active in the hardware. An active uart sirq shoudl be
enabled based on uart mapping configuration.

Signed-off-by: Venkataramana Kotakonda <venkataramana.kotakonda@intel.com>