* Enable DC calibration and crystal calibration on Centrino Advanced-N
6250 parts.
* Workaround for a HW bug (does not affect 4965AGN) that may sporadically
affect latency under some rare circumstances. From a similar commit to
iwlwifi.
* Update sensitivity settings for 5000 series to workaround a performance
bug in the DSP (1000 is not affected so we keep the old values for 5000).
* Update sensitivity settings for 6000 series.
* Set differential gains on 6250 too (but use a 1.0 factor, not 1.5).
* Init OFDM sensitivity with min value (which depends on the chip)
instead of hardcoding it to 90.
* Read calibration version from ROM and set IWN_GP_DRIVER_CALIB_VER6
bit on 6x50 if version >= 6.
Approved by: rpaulo (mentor)
Obtained from: OpenBSD
MFC after: 2 weeks
4019bb9309