cc/gcc: remove --enable-symver option

That option is coming from the original crosstool, and is not entirely
understand here.

Moreover, it breaks with newer gcc-s: 4.6.1 now breaks while configuring
libjava (and probably some other libs as well, untested).

There is an related bug report to the gcc BZ:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49555

If need be, the old behavior can be restored with:
CC_CORE_EXTRA_CONFIG_ARRAY="--enable-symver=gnu"
CC_EXTRA_CONFIG_ARRAY="--enable-symver=gnu"

Reported-by: Bryan Hundven <bryanhundven@gmail.com>
Reviewed-by: Bryan Hundven <bryanhundven@gmail.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
(transplanted from b24ead1a59472195f5b2071ff70664c36fa21c3f)

# Blackfin specific configuration file

config ARCH_blackfin

    select ARCH_SUPPORTS_32

    select ARCH_DEFAULT_32

    select ARCH_DEFAULT_LE

    select ARCH_SUPPORT_ARCH

    select ARCH_SUPPORT_CPU

    select ARCH_SUPPORT_TUNE

    select ARCH_SUPPORT_FPU

     help

      The Blackfin architecture