rockchip: update boot0 hook

rockchip: update boot0 hook

Rockchip SoCs only need boot0 hook at SPL, and the U-Boot proper do not
need it.

The very beginning of U-Boot proper is different between armv7 and armv8:
armv7 start with ARM_VECTORS while armv8 start with 'b reset'.

Here is the map of very beginning for all cases:
armv7 SPL: TAG(overwrite 'b 1f')+'b reset' + ARM_VECTORS
armv7 U-Boot: ARM_VECTORS
armv8 SPL: TAG(overwrite 'b 1f')+'b reset' + Reserved_iram(rk3399)
armv8 U-Boot: 'b reset'

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>