mwifiex: drop 'add_tail' param from mwifiex_insert_cmd_to_pending_q()

It's always called with 'true' -- we only determine it 'false' locally
within this function. So drop the parameter.

Also, this should be 'bool' (since we use true/false), not 'u32'.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>