wifi: plfxlc: remove redundant NULL-check for GCC 12

GCC is upset that we check the return value of plfxlc_usb_dev()
even tho it can't be NULL:

drivers/net/wireless/purelifi/plfxlc/usb.c: In function ‘resume’:
drivers/net/wireless/purelifi/plfxlc/usb.c:840:20: warning: the comparison will always evaluate as ‘true’ for the address of ‘dev’ will never be NULL [-Waddress]
  840 |         if (!pl || !plfxlc_usb_dev(pl))
      |                    ^

plfxlc_usb_dev() returns an address of one of the members of pl,
so it's safe to drop these checks.
Acked-by: Kalle Valo <kvalo@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/wireless/purelifi/plfxlc/usb.c

@@ -824,7 +824,7 @@ static int suspend(struct usb_interface *interface,
 	struct plfxlc_usb *pl = get_plfxlc_usb(interface);
 	struct plfxlc_mac *mac = plfxlc_usb_to_mac(pl);
 
-	if (!pl || !plfxlc_usb_dev(pl))
+	if (!pl)
 		return -ENODEV;
 	if (pl->initialized == 0)
 		return 0;
@@ -837,7 +837,7 @@ static int resume(struct usb_interface *interface)
 {
 	struct plfxlc_usb *pl = get_plfxlc_usb(interface);
 
-	if (!pl || !plfxlc_usb_dev(pl))
+	if (!pl)
 		return -ENODEV;
 	if (pl->was_running)
 		plfxlc_usb_resume(pl);