staging: greybus: audio: Fix sparse warning.

Sparse complains that:
   warning: restricted send_ctl_elem_iface_t degrades to integer.

I have looked at this code, and the code is fine as-is. Normally we
would frown on using the __force directive to silence Sparse warnings
but in this case it's fine. Case statements can't be made into __bitwise
types. We also can't change the type of "ctl->iface" either because that
is part of the user space API.

So just add a (__force int) to make the warning go away.

Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Rajat Asthana <thisisrast7@gmail.com>
Link: https://lore.kernel.org/r/20210519134119.848055-1-thisisrast7@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>