iwlwifi: support per-platform antenna gain

iwlwifi: support per-platform antenna gain

TX power limits as defined in the OTP assume the worst case scenario
in terms of the platform's atenna gain, but most platforms are below
that value so they can use more TX power without passing the regulatory
limit. If the platform indicates in the BIOS that it indeed has lower
gain, and the geographic location allows it, higher TX power can be
used. The driver reads the PPAG (Per-Platform Antenna Gain) data from
BIOS (if it exists), validates it and sends the appropriate command to
the FW. This flow happens once at FW init, in case of suspend/resume
there is no need to read again from BIOS as we save those values during
init, so just send the PPAG command again to FW.

Signed-off-by: Gil Adam <gil.adam@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>