ARM: imx: add i.mx6ulz msl support

The i.MX 6ULZ processor is a high-performance, ultra
cost-efficient consumer Linux processor featuring an
advanced implementation of a single Arm® Cortex®-A7 core,
which operates at speeds up to 900 MHz.

This patch adds basic MSL support for i.MX6ULZ, the
i.MX6ULZ has same soc_id as i.MX6ULL, and SRC_SBMR2 bit[6]
is to differentiate i.MX6ULZ from i.MX6ULL, 1'b1 means
i.MX6ULZ and 1'b0 means i.MX6ULL.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>