We can't use SAR Geo if basic SAR is not enabled, since the SAR Geo
tables define offsets in relation to the basic SAR table in use.
To fix this, make iwl_mvm_sar_init() return one in case WRDS is not
available, so we can skip reading WGDS entirely.
Fixes: a6bff3cb19 ("iwlwifi: mvm: add GEO_TX_POWER_LIMIT cmd for geographic tx power table")
Cc: stable@vger.kernel.org # 4.12+
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>