mwifiex: remove redundant pdev check in suspend/resume handlers

to_pci_dev() would just do struct offset arithmetic on struct
device to get 'pdev' pointer. We never get NULL pdev pointer.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Tested-by: Xinming Hu <huxm@marvell.com>
Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>