tests/tcg/s390x/console.c: directly implement memcpy and memset

pc-bios/s390-ccw/sclp.c uses memcpy and memset.
pc-bios/s390-ccw is part of QEMU repository.
However roms/SLOF is only available if submodules have been
initialized, which is not not always the case.

To break this dependency, just copy their definition here, and remove
include to submodules files.

Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>
Tested-by: Aniket Sahu <asahu1x@linux.ibm.com>
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>
Message-ID: <20260827221506.91574-86-pierrick.bouvier@oss.qualcomm.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>