tests/tcg: move architecture independent tests into subdir

tests/tcg: move architecture independent tests into subdir

We will want to build these for all supported guest architectures so
lets move them all into one place. We also drop test_path at this
point because it needs qemu utils and glib bits which is hard to
support for cross compiling.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>