iwlwifi: mvm: remove set but not used variable 'he_phy_data'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/wireless/intel/iwlwifi/mvm/rxmq.c: In function 'iwl_mvm_rx_mpdu_mq':
drivers/net/wireless/intel/iwlwifi/mvm/rxmq.c:1386:7: warning:
 variable 'he_phy_data' set but not used [-Wunused-but-set-variable]
   u64 he_phy_data;

'he_phy_data' never used since be introduce in
commit 18ead597

 ("iwlwifi: support new rx_mpdu_desc api")

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>