Add cpu type for i.MX6QP/DP.

This patch also fix is_mx6dqp(), since get_cpu_rev can return MXC_CPU_MX6QP
and MXC_CPU_MX6DP, we should use:
(is_cpu_type(MXC_CPU_MX6QP) || is_cpu_type(MXC_CPU_MX6DP)).

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Acked-by: Stefano Babic <sbabic@denx.de>