the application processor trampoline needs the trampoline physical
address to be mapped for the few instructions between loading the
page table and jumping to normal memory area; setup a new pt for them.
Also make it use its stack where it needs to be directly.
With that, x86 can finally remove the 0 page from its init mapping
Change-Id: Iab3f33a2ed22570eeb47b5ab6e068c9a17c25413