soc: swr-mstr: Fix headset not detetcted issue on devnum 0 detached

Headset is not detected if devnum 0 gets detached at bootup.
This is because on detach being called hw will mask interrupt
at slave side but will not unmask it afterwards.
Also device 0 is used only for discovery purpose and
interrupt shouldnt be masked if it detaches.

Change-Id: I78d47243ef67ea5ee1fe3badaec94e596bc8faf3
Signed-off-by: Vatsal Bucha <vbucha@codeaurora.org>