ASoC: ABE DAI: Call modem trigger in bespoke_trigger()

Modem DAI is a special case because requires explicit ALSA PCM
calls to the DAI associated with the serial port (e.g. McBSP).
The trigger() call was missing and the serial port was not
initiating any transfer.

Signed-off-by: Misael Lopez Cruz <misael.lopez@ti.com>