be2net: fix to get max VFs supported from adapter

The user supplied num_vfs value need not be compared
against a static BE_MAX_VF, but can be checked against
the actual VFs that the device can support.

Signed-off-by: Ajit Khaparde <ajit.khaparde@emulex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>