samples: update the rpi sample

And use the newly introduced CT_ARCH_SUFFIX at the same time. :-)

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 reporter_name="Remy Bohmer"

 reporter_url="linux@bohmer.net"

 reporter_comment="Example for building a toolchain for m68000 bare metal targets"