spl: spl_nand.c: Add NAND loading message

spl: spl_nand.c: Add NAND loading message

This patch adds a short message to the SPL NAND loader, which displays
the source and destinations addresses including the size of the
loaded image, like this:

U-Boot SPL 2019.04-rc3-00113-g486efd8aaf (Mar 15 2019 - 14:18:02 +0100)
Trying to boot from NAND
Loading U-Boot from 0x00040000 (size 0x000a0000) to 0x22900000

I find this message quite helpful - hopefully others do so as well.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Heiko Schocher <hs@denx.de>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Tom Rini <trini@konsulko.com>