MFC r318014, r318091, r318125, and r318263.

r318014:
cxgbe(4): Fixes related to the knob that controls link autonegotiation.

• Do not leak the adapter lock in sysctl_autoneg.
• Accept only 0 or 1 as valid settings for autonegotiation.
• A fixed speed must be requested by the driver when autonegotiation is disabled otherwise the firmware will reject the l1cfg command. Use the top speed supported by the port for now.

r318091:
cxgbe(4): Do not assume that if_qflush is always followed by inteface-down.

r318125:
Adjust whitespace and fix a comment. No functional change.

r318263:
cxgbe(4): netmap-only interrupts for a VI do not have an associated rxq
or ofld_rxq and should be ignored by vi_intr_iq.

Sponsored by: Chelsio Communications