fixup! arm: Add smp support and a simple smptest

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
arm: SMP thread_info support

Support a small per-cpu thread-info structure located at the bottom of
each stack page for each CPU.  This struct contains only the cpu_id for
now, but allows any code to call get_cpu_id() to get the current CPU id
of the exeuting processor.

Also expand the smptest framework to test that CPU0 and CPU1 report this
value as expected.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
arm: Add lib/arm/compiler.h

This is a simple file to add to built-in compiler options useful for all
sorts of test code.  We should have a structure where we had an
arch-generic compiler.h file which could automatically import an
arch-specific one, and the generic one could hold defines for gcc stuff
like 'noinline' and the arch-specific stuff could contain support for
stuff like arch_extensions, dsb etc. for ARM, for example.

Do with the ARM one for now.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
arm: Enable MMU support

Support enabling the MMU through an identity map to measure performance
in a more realistic scenario.  Also add a very limited simple test that
enabling the MMU seems to work on boot.  This test could be exanded to
some memory read/writes and to include some SMP support testing.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>