When Trimslice is booted from serial flash, the boot ROM does this, so
U-Boot doesn't need to. However, booting from the SD slot for recovery
purposes, the boot ROM does not set up the pinmux for serial flash. Add
code to U-Boot to set this up, so that an SD-based recovery U-Boot image
can upgrade the U-Boot in serial flash.
Signed-off-by: Stephen Warren <email@example.com>
Signed-off-by: Tom Warren <firstname.lastname@example.org>