imx: mx7ulp: Add soc level initialization codes and functions

Implement soc level functions to get cpu rev, reset cause, enable cache,
etc. We will disable the wdog and init clocks in s_init at very early u-boot
phase.

Since the we are seeking the way to get chip id for mx7ulp, the get_cpu_rev
is hard coded to a fixed value. This may change in future.

Reuse some code in imx-common.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Ye Li <ye.li@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
diff --git a/arch/arm/include/asm/arch-imx/cpu.h b/arch/arm/include/asm/arch-imx/cpu.h
index 8bd1421..b052406 100644
--- a/arch/arm/include/asm/arch-imx/cpu.h
+++ b/arch/arm/include/asm/arch-imx/cpu.h
@@ -25,10 +25,12 @@
 #define MXC_CPU_MX6QP		0x69
 #define MXC_CPU_MX7S		0x71 /* dummy ID */
 #define MXC_CPU_MX7D		0x72
+#define MXC_CPU_MX7ULP		0x81 /* Temporally hard code */
 #define MXC_CPU_VF610		0xF6 /* dummy ID */
 
 #define MXC_SOC_MX6		0x60
 #define MXC_SOC_MX7		0x70
+#define MXC_SOC_MX7ULP		0x80 /* dummy */
 
 #define CHIP_REV_1_0            0x10
 #define CHIP_REV_1_1            0x11