arm: add DEBUG_SET_MODULE_RONX option to Kconfig

Now that all the page setting infrastructure is in place,
Add the DEBUG_SET_MODULE_RONX to the ARM debugging Kconfig.
When turned on, data sections for modules will be marked as NX
and read only sections will be marked as such.

Change-Id: I8940410f8010ed7455deef59800a3f84bfab8b47
CRs-Fixed: 498398
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>