cxgbe(4): Update firmwares to 1.25.6.0.

cxgbe(4): Update firmwares to 1.25.6.0.

Changes since 1.25.0.0 are listed here.  This list comes from the
Release Notes for the "Chelsio Unified Wire v3.14.0.3 for Linux"
release dated 2021-05-21.

Fixes
-----

BASE:
- Fixed Back to back T6 100G-CR4 link coming up with NO FEC sometimes.
- [T5] Try to bring up link in 1G speed if link doesn't come up on 10G.
- Fixed a bug to not allow BaseR fec in 100G speed.
- Fixed linkup issues on BT adapter in 1G and 100M speed.
- Fixed an issue to allow driver to send VI_ENABLE multiple times (once
  with rx disable and then later rx enable).
- Fixed rate limiting not working on class number 16 to 30.
- Fixed backward compatibility issue in port type interpretation with vpd
  version 0x80.

ETH:
- Fixed a case when firmware failed to deliver NIC WR completion to host.
- No rate limit support for WR ETH_TX_PKTS2 due to performance reasons.

OFLD
- Fixed a connection hang in SO adapters when tp_plen_max (set by driver)
  is more than the window size.
- Added fw_filter_vnic_mode to firmware API file (t4fw_interface.h)
- Use correct rx channel in coprocessor crypto completion (CPL_FW6_PLD). This
  was causing out of order completion to host.

FOiSCSI
- Fixed a crash due to unaligned access of ipv6 address.
- Fixed a crash during lun reset.

Enhancements
------------

ETH:
- Rate limiting support added for encapsulated (vxlan, nvgre, geneve) NIC TCP
  packets.

OFLD:
- More than 128 SGLs supported in FW_RI_FR_NSMR_WR. Now, more than 16GB
  (upto 64GB) of PBLs can be written with single FW_RI_FR_NSMR_WR.

Obtained from:	Chelsio Communications
MFC after:	1 month
Sponsored by:	Chelsio Communications