cc/gcc: fix 128-bit long doubles option

Spotted by Arnaud LACOMBE:
http://sourceware.org/ml/crossgcc/2010-10/msg00122.html

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"