rockchip: bring TZRAM_SIZE values in line

The agreed upon division of early boot locations is 0x40000 for bl31
to leave enough room for u-boot-spl and 0x100000 for bl33 (u-boot).

rk3288 and rk3399 already correctly secure the ddr up to the 1MB boundary
so pull the other platforms along to also give the Rockchip TF-A enough
room to comfortably live in.

Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Change-Id: Ie9e0c927d3074a418b6fd23b599d2ed7c15c8c6f