staging: mt7621-mmc: Remove unused card_workqueue from msdc_host

The card_workqueue field of msdc_host is already if 0'd out and there
are no references to it in the code (not even in unused code), so
remove it.
Signed-off-by: Christian Lütke-Stetzkamp <christian@lkamp.de>
Reviewed-by: NeilBrown <neil@brown.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/mt7621-mmc/mt6575_sd.h

@@ -931,11 +931,7 @@ struct msdc_host {
 
 	int                         irq;            /* host interrupt */
 
-#if 0
-	struct work_struct		card_workqueue;
-#else
 	struct delayed_work		card_delaywork;
-#endif
 
 	struct completion           cmd_done;
 	struct completion           xfer_done;