hal: add support for I2S based external modem

There are specific xml files used for I2S based external modem.
Add check to load the correct xml file.

For I2S based external modem, voice sample rate can be 8k or
16k based on vocoder type. Call csd client api to get the
correct sample rate to configure voice call.

Change-Id: Ie9799336620f49a890355be74fe1830eb348cabe