mtd: rawnand: jz4740: Use the proper format specifier to print chipnr

In jz_nand_detect_bank(), chipnr is a size_t argument. Use %zu instead
of %i when printing it.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>