include: rk3328: Add default env for compressed kernel images

Add default memory addresses for kernel_comp_addr_r and kernel_comp_size
to enable booting from a compressed kernel image. This area is temporarily
used to decompress the kernel image on-the-fly.

Signed-off-by: Christopher Obbard <chris.obbard@collabora.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>