ipc: Added support for IPC interrupt mode

This patch adds support for ipc command interrupt mode.
Also added platform data option to select 'irq_mode'

irq_mode = 1: configure the driver to receive IOC interrupt
for each successful ipc_command.

irq_mode = 0: makes driver use polling method to
track the command completion status.

Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: David Cohen <david.a.cohen@linux.intel.com>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>