boards: qemu_x86: properly enable XIP

The '#if XIP' in the DTS file never worked properly,
causing the QEMU build to think it has much more RAM
then it actually has. If RAM overflowed, this would not
be caught by the build, instead there would be strange
crashes when the data copy takes place.

The QEMU targets themselves are not XIP, everything
is actually RAM, but the first 4 megabytes are
considered to be a memory-mapped flash region. This
is done to ensure that the XIP data copying infrastructure
doesn't bit-rot on x86. We are at the point where
a lot of things depend on this, so just select it in
the board Kconfig instead of enabling in the
defconfigs.

Fixes: #15835

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
5 files changed