mtd: *nftl: return -ENOMEM when kmalloc failed

The driver is using -1 instead of the -ENOMEM defined macro to
specify that a buffer allocation failed. Using the correct error
code is more intuitive

Smatch tool warning:
drivers/mtd/inftlmount.c:333 check_free_sectors() warn: returning -1
instead of -ENOMEM is sloppy
drivers/mtd/nftlmount.c:272 check_free_sectors() warn: returning -1
instead of -ENOMEM is sloppy

No functional change, just more standardized.

Reported-by: Abaci Robot <[e-mail]>
Signed-off-by: Yang Li <[e-mail]>
[<[e-mail]>: Fixed the title]
Signed-off-by: Miquel Raynal <[e-mail]>
Link: https://lore.kernel.org/linux-mtd/[e-mail]

drivers/mtd/inftlmount.c

···
 
 	buf = kmalloc(SECTORSIZE + mtd->oobsize, GFP_KERNEL);
 	if (!buf)
-		return -1;
+		return -ENOMEM;
 
 	ret = -1;
 	for (i = 0; i < len; i += SECTORSIZE) {

drivers/mtd/nftlmount.c

···
 
 	buf = kmalloc(SECTORSIZE + mtd->oobsize, GFP_KERNEL);
 	if (!buf)
-		return -1;
+		return -ENOMEM;
 
 	ret = -1;
 	for (i = 0; i < len; i += SECTORSIZE) {