virtio: fix overwritten driver flags

virtio: fix overwritten driver flags

The "drv_flags" is set with device as the input, which means different
device (say, modern vs legacy) could end up with a different value. And
the fact that "drv_flags" is shared by all devices means that every time
we add a new device, it simply overwrites the value configured from the
last device.

Therefore, when two virtio devices have different flags, it may lead to
wrong result, such as virtio would set irq config when it's not supported.

Making the flag per device (using "dev->data->dev_flags") could let us
have different value for each device, which would avoid the above issue.

Fixes: da978dfdc43 ("virtio: use port IO to get PCI resource")

Reported-by: David Marchand <david.marchand@6wind.com>
Suggested-by: David Marchand <david.marchand@6wind.com>
Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
Acked-by: David Marchand <david.marchand@6wind.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>