iwlwifi: mvm: rfi: don't lock mvm->mutex when sending config command

The mutex is already locked in iwl_mvm_mac_start.

Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Fixes: 21254908

 ("iwlwifi: mvm: add RFI-M support")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/iwlwifi.20210326125611.703288ea058d.I82a0312389032d07c3b478bef3e938e06bfa7df6@changeid