mx6sabreauto boards come with 32 MiB of parallel NOR flash.

Add support for it:

U-Boot 2015.01-rc1-18107-g1543636-dirty (Nov 14 2014 - 11:11:04)

CPU:   Freescale i.MX6Q rev1.2 at 792 MHz
Reset cause: POR
Board: MX6Q-Sabreauto revA
I2C:   ready
DRAM:  2 GiB
Flash: 32 MiB
NAND:  0 MiB

Due to pin conflict with I2C3, only define configure I2C3 IOMUX when flash is
not used.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>