exynos: artik10: resize CONFIG_TRUSTZONE_RESERVED_DRAM to 24MB

exynos: artik10: resize CONFIG_TRUSTZONE_RESERVED_DRAM to 24MB

This patch resizes trustzone reserved dram area
from 0x1600000 to 0x1800000.

For secure OS,
we want to reserve secure DRAM region as 24MB like below:

[Secure OS Memory Information for ARTIK10]

   --------------------- 0xC000_0000
        Secure OS
          (8MB)
   --------------------- 0xBF80_0000

       Frame Buffer
    (16MB, To be used)

   --------------------- 0xBE80_0000

Change-Id: Ie7c6ae569f0b5a7601bf2a4ffd6a25f0d857d196
Signed-off-by: Jaehoon Kim <jh228.kim@samsung.com>