imx: imx7d: initial arch level support

* Add system arch level header files
  - imx-regs.h: iMX7D SoC system architecture registers
  - crm_regs.h: Clock control module registers
  - sys_proto.h: helper callback function for SoC setup

Signed-off-by: Adrian Alonso <aalonso@freescale.com>
Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Signed-off-by: Ye.Li <B37916@freescale.com>