mwifiex: pcie: remove unnecessary 'pdev' check

'card->dev' is initialized once and is never cleared. Drop the
unnecessary "safety" check, as it simply obscures things, and we don't
do this check everywhere (and therefore it's not really "safe").

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