mtd mxc nand: Merge init functions

Merge mxc_setup_config1() into board_nand_init() in order to ease the addition
of i.MX5 support in the following patches.

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
Cc: Scott Wood <scottwood@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>
Signed-off-by: Scott Wood <scottwood@freescale.com>