misc: mic: Change mic_notify(...) to return true.

virtqueue_{kick()/notify()} methods are required to return bool due to
API changes introduced in commit 5b1bf7cb.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Sudeep Dutt <sudeep.dutt@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>