iwlwifi: mvm: add explicit check for non-data frames in get Tx rate

In roaming flows and during reassociation, its possible that data frames
such as EAPOLs for 4 way handshake/ 802.1x authentication are initially set
to higher MCS rate. Though these are pruned down to a lower legacy rate
before sending to the FW, driver also emits a kernel warning - intended for
non-data frames. Add checks to avoid such warnings for data frames, while
also enhancing the debug data printed.

Signed-off-by: Krishnanand Prabhu <krishnanand.prabhu@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210117164916.d9ded010c4ce.Ie1d5a33d7175c0bcb35c10b5729748646671da31@changeid


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