[PATCH net 0/3 RESEND] xen-netback: hash mapping handling adjustments

(re-send just to satisfy the apparent need for "net" inside the square brackets)

First and foremost the fix for XSA-270. On top of that further changes
which looked desirable to me while investigating that XSA.

1: fix input validation in xenvif_set_hash_mapping()
2: validate queue numbers in xenvif_set_hash_mapping()
3: handle page straddling in xenvif_set_hash_mapping()

Signed-off-by: Jan Beulich <redacted>