qemu/bswap: Add const_le64()

qemu/bswap: Add const_le64()

Gcc requires constant versions of cpu_to_le* calls.

Add a 64 bit version.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Gregory Price <gregory.price@memverge.com>
Tested-by: Gregory Price <gregory.price@memverge.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20230206172816.8201-9-Jonathan.Cameron@huawei.com>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>