MIPS: BCM63xx: improve CFE version detection

There are some CFE variants that start with 'cfe-vd' instead of 'cfe-v', such
as the one used in the Huawei HG556a: "cfe-vd081.5003". In this case, the CFE
version is stored as is (string vs number bytes).

Some newer devices have an additional version number, such as the Comtrend
VR-3032u: "1.0.38-112.118-11".

Finally, print the string as is if the version doesn't start with "cfe-v" or
"cfe-vd", but starts with "cfe-".

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>