rockchip: rk3568: Read cpuid from otp

The cpuid on RK3568 is located at 0xa instead of 0x7 as all other SoCs.
Add and use a CFG_CPUID_OFFSET to define this offset.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>