x86: Make .rodata readonly
x86: Make .rodata readonly

During the conversion of .bin to .o objcopy was not setting the
section to be readonly causing the .rodata in the final image has
write permission.

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

GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,nashif/zephyr,galak/zephyr,finikorg/zephyr,nashif/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr