ARM: 7827/1: highbank: fix debug uart virtual address for LPAE

Section entries are 2MB on LPAE, so the DEBUG_LL virtual address must
have the same offset in the 2MB section as the physical address. This
fixes async external aborts when DEBUG_LL is enabled on Midway.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>