arch: x86: Use macro BIT to shift bits
arch: x86: Use macro BIT to shift bits

The operation was shifiting bit using a signed constant in the left
operand. Use BIT macro to do it properly.

MISRA-C rule 12.2

Signed-off-by: Flavio Ceolin <979b9165500b0741b9d0500e2efd74fc1547bff7@intel.com>

galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,nashif/zephyr,punitvara/zephyr,explora26/zephyr,finikorg/zephyr,nashif/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,finikorg/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,explora26/zephyr,Vudentz/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,ldts/zephyr,explora26/zephyr,nashif/zephyr,ldts/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,Vudentz/zephyr,ldts/zephyr,punitvara/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,punitvara/zephyr