mtd: nand: remove nand size print from nand_init function

Add nand_size() function to move the nand size print into initr_nand().
Remove nand size print from nand_init() to allow other function to call
nand_init() without printing nand size.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>