MFC r253701, r253829, r253873, r253889, r253890, r254577, r254727, and r254933.

r253701:
Display a string instead of a numeric code in the linkdnrc sysctl.

r253829:
Display SGE tunables in the sysctl tree.

dev.t5nex.0.fl_pktshift: payload DMA offset in rx buffer (bytes)
dev.t5nex.0.fl_pad: payload pad boundary (bytes)
dev.t5nex.0.spg_len: status page size (bytes)
dev.t5nex.0.cong_drop: congestion drop setting

r253873:
Set up congestion manager context properly for T5 based cards.

r253889:
Fix previous commit (r253873).  "cong" has one bit per channel but the
congestion channel map has 1 nibble per channel.  So bits wxyz need to
be blown up into 000w000x000y000z.

r253890:
Display temperature sensor data.  Shows -1 if sensor not
available on the card.

# sysctl dev.t4nex.0.temperature
# sysctl dev.t5nex.0.temperature

r254577:
Display P/N information in the description.

r254727:
There is no need to hold the freelist lock around alloc/free of
software descriptors.  This also silences WITNESS warnings when
the software descriptors are allocated with M_WAITOK.

r254933:
Use correct mailbox and PCIe PF number when querying RDMA parameters.