accel/tcg: move atomic_template.h to accel/tcg/

Signed-off-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: NThomas Huth <thuth@redhat.com>
Message-Id: <20170911213328.9701-5-f4bug@amsat.org>
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>