Decreases code size of the nand_spl

The canyonland boards nand_spl size is just under the maximum 4KByte size. This
patch decreases the size of the nand_spl to make a previous commit - commit
65a9db7b - fit in the nand_spl.

Signed-off-by: Alex Waterman <awaterman@dawning.com>
Acked-by: Stefan Roese <sr@denx.de>
Signed-off-by: Scott Wood <scottwood@freescale.com>