ath10k: fix legacy rate packet debug messages

Legacy rate packets may not necessarily be having a rx status
flag of '0' always, for example management frame have flags
like RX_FLAG_ONLY_MONITOR / RX_FLAG_MACTIME_END also set

Just check 'VHT' and 'HT' flags are not set , and simply clasify it as
legacy rate packets

Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>