iwlwifi: mvm: remove useless debug message from RX

This message is useless - it's in the good case that always
happens so enabling it doesn't really help. Just remove it.
There are other ways to debug this (e.g. tracing) so there's
no need to add a message in the bad case.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>