mtd: nand: denali: remove unused struct member denali_nand_info::idx

The struct member "idx" was used as an index for debug_array long
ago, but the DEBUG_DENALI feature was removed by commit 7cfffac06ca0
("nand/denali: use dev_xx debug function to replace nand_dbg_print
and some printk"). Since then, this has been only initialized, but
never referenced.

Signed-off-by: Masahiro Yamada <[e-mail]>
Reviewed-by: Marek Vasut <[e-mail]>
Signed-off-by: Boris Brezillon <[e-mail]>

drivers/mtd/nand/denali.c

···
 /* initialize driver data structures */
 static void denali_drv_init(struct denali_nand_info *denali)
 {
-	denali->idx = 0;
-
 	/* setup interrupt handler */
 	/*
 	 * the completion object will be used to notify

drivers/mtd/nand/denali.h

···
 	spinlock_t irq_lock;
 	uint32_t irq_status;
 	int irq_debug_array[32];
-	int idx;
 	int irq;
 
 	uint32_t devnum;	/* represent how many nands connected */