If we set amsdu_len one after another the second one overwrites
the orig_amsdu_len so allow only moving from debug to non debug state.

Also the TLC update check was wrong: it was checking that also the orig
is smaller then the new updated size, which is not the case in debug
amsdu mode.
Signed-off-by: Mordechay Goodstein <mordechay.goodstein@intel.com>
Fixes: af2984e9 ("iwlwifi: mvm: add a debugfs entry to set a fixed size AMSDU for all TX packets")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200424182644.e565446a4fce.I9729d8c520d8b8bb4de9a5cdc62e01eb85168aac@changeid