integrator: make flash writeable on boot

This reconfigures the EBI (External Bus Interface) on the
integrator so that chip select 1, handling the flash memory, is
set to writeable. Without this it is not possible for U-Boot to
access flash memory and it crashes on startup since CFI won't
work properly.

Since this is the first time we use the EBI, we create a header
file for its registers.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>