The Barebox recognized false bad erase blocks while booting from a
Spansion NAND (1). This error occurred due a to high clock. The
Kernel sets the default NAND clock to 22Mhz. So, to fix this error and
to be more identical with the Kernel, the Barebox should be too.

1: nand: NAND device: Manufacturer ID: 0x01, Chip ID: 0xd3 (AMD/Spansion
S34ML08G2), 1024MiB, page size: 2048, OOB size: 128

Signed-off-by: Daniel Schultz <d.schultz@phytec.de>
Tested-by: Stefan Lengfeld <s.lengfeld@phytec.de>
Signed-off-by: Christian Hemp <c.hemp@phytec.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>