kernel.h: move includes to the top
kernel.h: move includes to the top

We need to start enforcing everywhere that kernel.h depends on
arch/cpu.h and any header included in the arch/cpu.h space cannot
depend on kernel.h.

Signed-off-by: Andrew Boie <aab045b28152628be6af0e556050d0381fd0a34d@intel.com>

mbolivar/zephyr,zephyriot/zephyr,finikorg/zephyr,kraj/zephyr,Vudentz/zephyr,ldts/zephyr,Vudentz/zephyr,punitvara/zephyr,Vudentz/zephyr,punitvara/zephyr,punitvara/zephyr,nashif/zephyr,Vudentz/zephyr,aceofall/zephyr-iotos,GiulianoFranchetto/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyriot/zephyr,aceofall/zephyr-iotos,explora26/zephyr,explora26/zephyr,galak/zephyr,ldts/zephyr,finikorg/zephyr,punitvara/zephyr,zephyriot/zephyr,ldts/zephyr,nashif/zephyr,kraj/zephyr,Vudentz/zephyr,mbolivar/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,aceofall/zephyr-iotos,nashif/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,mbolivar/zephyr,aceofall/zephyr-iotos,kraj/zephyr,GiulianoFranchetto/zephyr,zephyriot/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,mbolivar/zephyr,galak/zephyr,kraj/zephyr,punitvara/zephyr,galak/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,mbolivar/zephyr,zephyrproject-rtos/zephyr,zephyriot/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,explora26/zephyr,ldts/zephyr,nashif/zephyr,aceofall/zephyr-iotos,explora26/zephyr,GiulianoFranchetto/zephyr