This moves all the code to handle hyp mode to hypervisor-stub.S.
It simplifies the code as we now return if we were in hyp mode from
hypervisor_stub_vect_install allowing this value to be written directly
to the variable.
While here remove old macros for gcc 4.2.1 as it's too old to build
FreeBSD now we use the ARM EABI with hard float.