arm: Turn of d-cache before i-cache

arm: Turn of d-cache before i-cache

Booting the kernel fails on RK3288 (and probably other rockchip SoCs)
when the i-cache is disabled/flushed before d-cache.

I have not investigated whether this is due to U-Boot hanging or whether
it's very early in the linux boot, but following the approach of the
various rockchip U-Boot forks (first disable d-cache then i-cache) makes
things work.

Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>