gen_isr_tables: make vector offset a hidden option

If this is set incorrectly things will break all over the place.
Needs a default defined per-arch and left alone.

Change-Id: I3f8c842937a240297ee21589a22a7a9e51dbdfad
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
1 file changed