iwlwifi: mvm: add RFI-M support

RF Interference Mitigation is a new feature targeted to handle the
problem of interference between DDR memory and WiFi. The role of
the driver is to configure FW with the table holding a mapping
between problematic channels/bands and the corresponding frequencies.

This patch adds RFI infrastructure and adds two debugfs hooks:
- send RFI configuration command (currently with a default table) which
  will reset feature in the FW
- read the table, used by the FW (which can be a subset of the table
  that driver sent).

Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210210171218.2cea55a09bc7.I634b79795abad499ce442631d6672ffef8fc6d41@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>