virtio: fix query of legacy features

virtio: fix query of legacy features

Declare dst as type uint32_t instead of uint64_t, otherwise, we will get
a random upper 32 bit feature bits, as the following io port read reads
lower 32 bit only. It could lead a feature bits that include VIRTIO_F_VERSION_1
(the 32th bit) for legacy virtio, which is obviously wrong.

Fixes: b8f04520ad71 ("virtio: use PCI ioport API")

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