mtd: maps: physmap: Use dev_notice() and a %pR specifier

Replace printk(KERN_NOTICE) by dev_notice() use the %pR specifier to
print the iomem resource.

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>