virtio/vsock: add SEQPACKET receive logic

Update current receive logic for SEQPACKET support: performs
check for packet and socket types on receive(if mismatch, then
reset connection). Increment EOR counter on receive. Also if
buffer of new packet was appended to buffer of last packet in
rx queue, update flags of last packet with flags of new packet.

Signed-off-by: Arseny Krasnov <arseny.krasnov@kaspersky.com>
Signed-off-by: David S. Miller <davem@davemloft.net>