be2net: fixup TX-rate setting code for Skyhawk-R

Skyhawk-R FW supports TX-rate setting only as a % value of the link
speed, set via the SET_PROFILE_CONFIG cmd.

This patch makes the necessary changes to the FW cmd descriptors to support
the above change and also introduces checks in be_set_vf_tx_rate() to allow
only discrete values (that map to % of the link-speed).

Signed-off-by: Sathya Perla <sathya.perla@emulex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>