tests/tcg/multiarch: move the system memory test

There is nothing inherently architecture specific about the memory
test although we may have to manage different restrictions of
unaligned access across architectures.

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

diff --git a/tests/tcg/i386/system/memory.c b/tests/tcg/multiarch/system/memory.c
similarity index 100%
rename from tests/tcg/i386/system/memory.c
rename to tests/tcg/multiarch/system/memory.c