Add the version number to the iwl_geo_tx_power_profile_cmd structs and
move the union into a common place.  Additionally, reuse the code that
sets elements that are at the same place in the struct across
different versions.

While at it remove an unused variable, add a comment and move the v2
specific element setting to inside the if statement.  Additionally,
invert the if for slightly more readability.
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200928121852.23ec241f16cd.I8cd21fc5a2498e820b50e1f49a4cbfe545afe30e@changeidSigned-off-by: Luca Coelho <luciano.coelho@intel.com>