ARM: dts: msm: Update external image memory node for tbase

Current TZ apps region is not sufficient to run the tbase app. TZ
apps region has to increase to accommodate tbase. This patch update
the external image memory node details to increase TZ apps region.

Change-Id: I5a12309a355691dc99182eb95fdf1aa188c3e600
Signed-off-by: AnilKumar Chimata <anilc@codeaurora.org>