iwlwifi: mvm: don't send GEO_TX_POWER_LIMIT to old firmwares

Old firmware versions don't support this command. Sending it
to any firmware before -41.ucode will crash the firmware.

This fixes https://bugzilla.kernel.org/show_bug.cgi?id=201975

Fixes: 66e83903

 ("iwlwifi: fix wrong WGDS_WIFI_DATA_SIZE")
CC: <stable@vger.kernel.org> #4.19+
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>