configure: do not require cvs

cvs is used to get newlib directly from its repository. Missing cvs
will only allow getting newlib from the released tarballs.

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

 reporter_name="Remy Bohmer"

 reporter_url="linux@bohmer.net"

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