arm: mvebu: Fix internal register config on A38x

Currently booting on A38x is broken. As the current code tries to detect
the SoC family to disable the MMU for the A38x at runtime. But before the
internal registers are switched to the new location (0xf100.0000), this
runtime detection does not work. As all macros / defines are already
assigned to the new location at 0xf100.0000. But the registers are sill
mapped to the default location at 0xd000.0000.

This patch now makes sure, no such runtime detection is used before
the internal registers are configured to the new location. After this,
the remaining cache cleanup is executed.

Signed-off-by: Stefan Roese <sr@denx.de>
Reported-by: Kevin Smith <kevin.smith@elecsyscorp.com>
Cc: Luka Perkov <luka.perkov@sartura.hr>