drivers: ieee802154: cc2520: Fix compiler warning
drivers: ieee802154: cc2520: Fix compiler warning

The stack address was incorrectly specified when stack usage
was being debugged. This caused compiler to emit this warning

drivers/ieee802154/ieee802154_cc2520.c:1136:16: warning:
    dereferencing type-punned pointer will break strict-aliasing
    rules [-Wstrict-aliasing]
       ((struct cc2520_context *)(&__device_cc2520))->
                ^

Signed-off-by: Jukka Rissanen <f9f077d1da4c7aa947f9864fa5a28c3588f6a45d@linux.intel.com>

mbolivar/zephyr,mbolivar/zephyr,runchip/zephyr-cc3220,ldts/zephyr,finikorg/zephyr,explora26/zephyr,fbsder/zephyr,ldts/zephyr,nashif/zephyr,Vudentz/zephyr,punitvara/zephyr,kraj/zephyr,nashif/zephyr,finikorg/zephyr,kraj/zephyr,mbolivar/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,mbolivar/zephyr,fbsder/zephyr,galak/zephyr,galak/zephyr,runchip/zephyr-cc3220,GiulianoFranchetto/zephyr,kraj/zephyr,finikorg/zephyr,finikorg/zephyr,punitvara/zephyr,Vudentz/zephyr,aceofall/zephyr-iotos,ldts/zephyr,Vudentz/zephyr,zephyriot/zephyr,Vudentz/zephyr,fbsder/zephyr,runchip/zephyr-cc3220,explora26/zephyr,kraj/zephyr,galak/zephyr,aceofall/zephyr-iotos,galak/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyriot/zephyr,aceofall/zephyr-iotos,explora26/zephyr,punitvara/zephyr,fbsder/zephyr,zephyriot/zephyr,zephyriot/zephyr,runchip/zephyr-cc3220,kraj/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,mbolivar/zephyr,ldts/zephyr,ldts/zephyr,nashif/zephyr,aceofall/zephyr-iotos,GiulianoFranchetto/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,zephyriot/zephyr,zephyrproject-rtos/zephyr,fbsder/zephyr,punitvara/zephyr,explora26/zephyr,aceofall/zephyr-iotos,GiulianoFranchetto/zephyr,nashif/zephyr,explora26/zephyr,runchip/zephyr-cc3220,nashif/zephyr