nand_spl: nand_boot.c: Remove last CONFIG_SYS_NAND_READ_DELAY occurance

Remove the last CONFIG_SYS_NAND_READ_DELAY occurance from nand_boot.c.
I missed this one in patch a9c847cb [nand_spl: nand_boot.c: Remove
CONFIG_SYS_NAND_READ_DELAY].

This fixes a compile breakage on kilauea_nand for example.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Scott Wood <scottwood@freescale.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>