virtio.h: add some user-friendly apis

[CV-Bowen]

• virtio.h: add new api virtio_has_feature()

virtio_has_feature() can be easily used to heck if the virtio device
support a specific feature.

And assgin feature to vdev->feature for virtio device role when get
features, so the virtio device side can use virtio_has_featrue() to
check weather the virtio device support a feature.

• virtio.h: add new feature bit VIRTIO_F_ANY_LAYOUT

Follow the virtio spec, this feature bit indicates that the device
accepts arbitrary descriptor layouts.

[CV-Bowen]

@arnopo Hi, I meet a CI issue:

#define virtio_read_config_member(vdev, structname, member, _ptr) \
	virtio_read_config((vdev), metal_offset_of(structname, member), \
			   _ptr, sizeof(*(_ptr)))

This code reports MACRO_ARG_REUSE: Macro argument reuse '_ptr' - possible side-effects?
So can we use typeof to avoid this issue?

[CV-Bowen]

@glneo @arnopo Please review again.

[CV-Bowen]

@arnopo Done, please review again.

[arnopo]

My apologies for this late review. Don't hesitate to ping us if you don't see activity after 2 or 3 weeks.

In addition of my comment could you please rework your commit title
replacing virtio.h by lib: virtio

[arnopo]

We should also check the feature_bit value. For time being we support only up to 32 features bit
so we should check that feature_bit < sizeof(features)