scsi: megaraid: Fix set but unused variable

In megadev_ioctl(), if MEGA_HAVE_STATS is not defined, the variables
num_ldrv and ustats are unused. Conditionally define them to avoid compiler
warnings.

Link: https://lore.kernel.org/r/20200706123351.451959-1-damien.lemoal@wdc.comSigned-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/megaraid.c

@@ -2975,14 +2975,13 @@ megadev_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
 	void		*data = NULL;	/* data to be transferred */
 	dma_addr_t	data_dma_hndl;	/* dma handle for data xfer area */
 	megacmd_t	mc;
-	megastat_t	__user *ustats;
-	int		num_ldrv;
+#if MEGA_HAVE_STATS
+	megastat_t	__user *ustats = NULL;
+	int		num_ldrv = 0;
+#endif
 	u32		uxferaddr = 0;
 	struct pci_dev	*pdev;
 
-	ustats = NULL; /* avoid compilation warnings */
-	num_ldrv = 0;
-
 	/*
 	 * Make sure only USCSICMD are issued through this interface.
 	 * MIMD application would still fire different command.