linux-user: fix translation of statx structures

All timestamps were copied to atime instead of to their respective
fields.

Fixes: efa92184 ("linux-user: Add support for translation of statx() syscall")
Signed-off-by: Ariadne Conill <ariadne@dereferenced.org>
Reviewed-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20191122174040.569252-1-ariadne@dereferenced.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>