bnx2x: Clean before update RSS arrives

When a PF receives a VF message indicating a change in RSS properties
it should clean the flags' bit-fields; Otherwise, it's possible that
some random values will be considered as flags by the lower layers configuring
the RSS in FW.

Signed-off-by: Michal Kalderon <michals@broadcom.com>
Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>