mtd: lpddr2_nvm: Fix possible null-ptr-deref

It will cause null-ptr-deref when resource_size(add_range) invoked,
if platform_get_resource() returns NULL.

Fixes: 96ba9dd65788 ("mtd: lpddr: add driver for LPDDR2-NVM PCM memories")
Signed-off-by: Hui Tang <[e-mail]>
Acked-by: Uwe Kleine-König <[e-mail]>
Signed-off-by: Miquel Raynal <[e-mail]>
Link: https://lore.kernel.org/linux-mtd/[e-mail]

drivers/mtd/lpddr/lpddr2_nvm.c

···
 
 	/* lpddr2_nvm address range */
 	add_range = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!add_range)
+		return -ENODEV;
 
 	/* Populate map_info data structure */
 	*map = (struct map_info) {