Asoc: swr: Handle MBHC and IRQ interrupts from tx slave

Interrupts will be handled by slave driver. This
needs slave pointer to store virtual interrupt and
pass it as a parameter to handle_nested_irq.

Change-Id: I356102a04b4fda7e5863f809cd848d7a82b82f36
Signed-off-by: Vatsal Bucha <vbucha@codeaurora.org>