virtio: Add module driver macro for virtio drivers.
virtio: Add module driver macro for virtio drivers.

Add helper macro for drivers that don't do anything
special in module init/exit.

Signed-off-by: Sjur Brændeland <90c9f68dc7b20ac89683f2c4f55e4a05e8dbf9ad@stericsson.com>
Signed-off-by: Rusty Russell <df9728c9e5104131c08c7adb03af425394842596@rustcorp.com.au>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas